Devon’s teacher requires that students show each step in solving a problem. Devon wrote the following when solving the equation x- 7 = 20:
x -7 = 20
x -7 = 20 + 7
x = 27
The teacher said that Devon’s work was not shown correctly. Why?
A) Devon’s final answer should be 13
B) Devon should have shown that he added 7 to both sides
C) Devon should have shown that he subtracted 7 from both sides
D) Devon should have shown that he added 7 to the left side only