Solve for b.

r = x(a + b)

b = (r-a)/x
b = (a-rx)/x
b = (r-ax)/x

Solving the equation for B, we obtain B=(R-Ax)/x (Third option)

Solution:

R=x(A+B)

Solving for B: Dividing both sides of the equation by x:

R/x=x(A+B)/x

R/x=A+B

Subtracting A both sides of the equation:

R/x-A=A+B-A

R/x-A/1=B

B=R/x-A/1

Subtracting the fractions on the right side of the equation:

B=(R-Ax)/x

the answer is a and d

it's either a or c hope this .