Answer:
![\boxed{ \boxed{ \bold{ \sf{d = 15}}}}](https://img.qammunity.org/2021/formulas/mathematics/high-school/8wr5s41wtgdufxezpisqsbxpnpw4d8s4qx.png)
Explanation:
![\sf{d - 7 = 8}](https://img.qammunity.org/2021/formulas/mathematics/high-school/qzn3oojdkdum4a19sh70srqibrsa50pdmr.png)
Move constant to right hand side and change it's sign
⇒
![\sf{d = 8 + 7}](https://img.qammunity.org/2021/formulas/mathematics/high-school/45kk2c5pu6a3rgh2igurf61mlbqscv4x6p.png)
Add the numbers
⇒
![\sf{d = 15}](https://img.qammunity.org/2021/formulas/mathematics/high-school/628ovo381bdhlzx0imp9id0rawxtgkhnbz.png)
Let's check:
When d = 15 , R.H.S = 15 - 7 = 8
And L.H.S = 8
Thus , R.H.S = L.H.S when d = 15.
Therefore d = 15 is the solution of the equation.
Hope I helped!
Best regards!