1. a - b = 3, i.e. b = a - 3.
2. b = 4a - 2
a - 3 = 4a - 2, i.e. -3 + 2 = 4a - a.
4a - a = 3a and -3 + 2 = -1, i.e. 3a = -1, hence a = -1/3 and b = -1/3 - 3 = -10/3.
∴ (a, b) = (-1/3, -10/3)
Johnny did NOT use the elimination method - he used substitution:
3(a-b)=9
4a=b+2
a - b = 3
4a - b = 2
I'm going to multiply the first equation by -1, then add the two equations:
-a + b = -3
4a - b = 2
3a = -1
a = -1/3
Now substitute a into either equation to find b.