Answer:
a = (r/x) -b
x = -14
Step-by-step explanation:
r=x(a+b)
Divide each side by x
r/x = a+b
Subtract b
r/x -b = a
x/2=-7
Multiply each side by 2
x/2*2 = -7*2
x = -14
It was $930.
To over check, multiply it by 20% , you will get $186.
Hope this helps !