To evaluate functions for the given value, we will substitute the mentioned value for x into the function given.

Let us see some example problems.

Find the value of
y given rule :

**Example 1 :**

y = 8x+5

when (i) x = 3 (ii) x = 7 (iii) x = 10 1/2

**Solution :**

Given rule, y = 8x+5

(i) when x = 3

By applying x = 3 in given rule, we get

y = 8x+5

y = 8(3)+5

y = 24+5

y = 29

Therefore, the value of y is 29

(ii) x = 7

By applying x = 7 in given rule, we get

y = 8x+5

y = 8(7)+5

y = 56+5

y = 61

Therefore, the value of y is 61

(iii) x = 10 1/2

Since the value of x is mixed fraction, we convert it into improper.

10 1/2 = 13/2

By applying x = 13/2 in given rule, we get

y = 8x+5

y = 8(13/2)+5

y = 52+5

y = 57

Therefore, the value of y is 57

**Example 2 :**

y = 21-4x

when (i) x = 0 (ii) x = 2 1/2 (iii) x = 7

**Solution :**

Given rule, y = 21-4x

(i) x = 0

By applying x = 0 in given rule, we get

y = 21-4x

y = 21-4(0)

y = 21

Therefore, the value of y is 21

(ii) x = 2 1/2

Converting the mixed fraction into improper fraction,

2 1/2 = 5/2

By applying x = 5/2 in given rule, we get

y = 21-4x

y = 21-4(5/2)

y = 21-10

y = 11

Therefore, the value of y is 11

(iii) x = 7

By applying x = 7 in given rule, we get

y = 21-4x

y = 21-4(7)

y = 21-28

y = -7

Therefore, the value of y is -7

**Example 3 :**

y = (3x+4)/2

when (i) x = 2 (ii) x = 6 (iii) x = 11

**Solution :**

Given rule, y = (3x+4)/2

(i) x = 2

By applying x = 2 in given rule, we get

y = (3x+4)/2

y = [3(2)+4]/2

y = (6+4)/2

y = (10/2)

y = 5

Therefore, the value of y is 5

(ii) x = 6

By applying x = 6 in given rule, we get

y = (3x+4)/2

y = [3(6)+4]/2

y = (18+4)/2

y = (22/2)

y = 11

Therefore, the value of y is 11

(iii) x = 11

By applying x = 11 in given rule, we get

y = (3x+4)/2

y = [3(11)+4]/2

y = (33+4)/2

y = (37/2)

y = 18.5

Therefore, the value of y is 18.5

**Example 4 :**

y = 2(x+3)-1

when (i) x = 4 (ii) x = 0 (iii) x = 6 1/2

**Solution :**

Given rule, y = 2(x+3)-1

(i) x = 4

By applying x = 4 in given rule, we get

y = 2(x+3)-1

y = 2(4+3)-1

y = 2(7)-1

y = 14-1

y = 13

Therefore, the value of y is 13

(ii) x = 0

By applying x = 0 in given rule, we get

y = 2(x+3)-1

y = 2(0+3)-1

y = 2(3)-1

y = 6-1

y = 5

Therefore, the value of y is 5

(iii) x = 6 1/2

Changing into mixed fraction, we get

6 1/2 = 13/2

By applying x = 13/2 in given rule, we get

y = 2(x+3)-1

y = 2(13/2+3)-1

y = 2(19/2)-1

y = 19-1

y = 18

Therefore, the value of y is 18.

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