20 and 45x
We look for a number that can go into both numbers.
5 into 20 is 4 and 5 into 45x is 9x.
5: 20 45x
4 9x
So no other number can go into 4 and 9x again.
So the GCF of 20 and 45x is 5.
Hope this explains it.
You can buy 4 shirts because you bought one pair of jean (80 - 29 = 51) and so with the leftover money you could buy 4 shirts because (12 x 4 = 48) and then you'd have a leftover 3 dollars.
slope = (6 - 1)/(-2 - 1) = 5/-3 = -5/3
Equation
y - 6 = -5/3 (x + 2)
Hope it helps