Given
43 - 3d= d + 9
Solution
Add 3d to both sides of the equal sign
43 = d + 3d + 9
43 = 4d + 9 Subtract 9 from both sides
43 - 9 = 4d Collect like terms on the left
34 = 4d Divide by 4 on both sides.
34/4 = 4d/4
8 2/4 = d
d = 8 2/4 = 8 1/2 = 8.5
Check
LHS
43 - 3 * 8.5
43 - 25.5
17.5
RHS
d + 9
8.5 + 9
17.5
and the problem checks.
C is the answer