Answer:
3x7
Step-by-step explanation:
7 + 7 + 7 is 3 x 7 because 7x3=21 and 7+7+7=21
X=3,-2 you solve by using the quadratic formula
Answer:
![\boxed{ \boxed{ \bold{ \sf{d = 15}}}}](https://tex.z-dn.net/?f=%20%5Cboxed%7B%20%5Cboxed%7B%20%5Cbold%7B%20%5Csf%7Bd%20%3D%2015%7D%7D%7D%7D)
Step-by-step explanation:
![\sf{d - 7 = 8}](https://tex.z-dn.net/?f=%20%5Csf%7Bd%20-%207%20%3D%208%7D)
Move constant to right hand side and change it's sign
⇒![\sf{d = 8 + 7}](https://tex.z-dn.net/?f=%20%5Csf%7Bd%20%3D%208%20%2B%207%7D)
Add the numbers
⇒![\sf{d = 15}](https://tex.z-dn.net/?f=%20%5Csf%7Bd%20%3D%2015%7D)
<u>Let's </u><u>check</u><u>:</u>
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!