Answer:
54
Explanation:
4x+7=18
subtracting 7 from both side of the equation
4x+7- 7=18 - 7
4x = 11
to find value of x , we divide both side of the equation by 4
4x/4 = 11/4 = 2.75
x = 2.75
now we plug in the found value of x = 2.75 in place of x in equation 12x+21
12*2.75 + 21 = 33 + 21 = 54
Thus, answer is 54