(3d+1)+(6d+8)=90 3d+1+6d+8=90 9d+9=90 -9 -9 9d=81 divide by 9 on both sides d=9
Explanation: In order to solve for d, you will need to remove the parentheses, then combine like variables. Then, subtract 9 from both sides. Finally, divide by 9 on both sides. You should get d=9.