A plus b equals 8 and a minus b equals 9?

Answer 1

Solve one of the formulas for A, then substitute that into the other formula to solve for B, then substitute the solution for B into one of the formulas to solve for A.

Here is how:

Givens:

A+B=8

A-B=9

So:

If A+B=8 then A=8-B

Next, substitute this into the other formula...

A-B=9

(8-B)-B=9

(-B) - B = 1

(-2B) = 1

B= (- 1/2)

Next, substitute the solution for B into one of the formulas to solve for A....

A+B=8

A+ (-1/2) = 8

A = 8 and 1/2

So...

B= (- 1/2)

A = 8 and 1/2