Fill in the blank with a variable term so that the given value of the variable will make the equation true.
a. +4=12; x=8
b. +4=12; x=4

a. x + 4 = 12; x = 8

b. 2x + 4 = 12; x = 4

Step-by-step explanation:

a. for x = 8; let unknown be k

k + 4 = 12

k = 12 - 4 = 8

k/x = 8/8 = 1 which is the coefficient of x

therefore x + 4 = 12 when x = 8 is correct

b. for x = 4

k + 4 = 12

k = 8

k/x = 8/4 = 2 which is the coefficient of x

therefore 2x + 4 = 12 when x = 4 is correct