Question

solve this sum in trial and error method = 3(x+4)=21
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Answer 1

3(x+4)=21

3x+12=21

3x=21-12

3x=9

x=9/3

x=3(Answer)

Hope it will help you

Answer 2

Putting x=1,

3(x+4) = 3 x 5 = 15

Putting x = 2,

3(x+4) = 3 x 6 =18

Putting x=3,

3(x+4) = 3 x 7 =21

Value of x =21