Question

Two equations are given below:

a − 3b = 9
a = b − 3

What is the solution to the set of equations in the form (a, b)?

(−9, −6)

(−4, −3)

(−6, −3)

(−9, −7)

Answer 1

The first one, (-9,-6) because if you were to plug it in the answers would equal therefore, the equation is true.

Answer 2

a is given to us so just plug a into the first equation:

b-3 - 3b =9

Add 3 to both sides:

b-3b=12

Combine like terms:

-2b=12

Divide by -2 to get b by itself:

b=-6

The only answer with b as -6 is the first one, (-9,-6)