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)?

Answer 1

Use substitution and put b-3 where a is in the first equation

Answer 2

A-3b=9
a=b-3

b-3-3b=9
-2b-3=9
-2b=12
2b=-12
b=-6

a=-6-3
a=-9

Solution: (-9,-6)
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Check: 
-9=-6-3
-9=-9
TRUE