Please solve this I am sooo confused help meeeee please please please. I will give you 15 points.

Solve the system of the equations:

a.)
3(x+y)−7=12x+y
6(y−2x)−1=−45x

b.)
5(x+2y)−3=3x+5
4(x−3y)−50=−33y

c.)
4x+1=5(x−3y)−6
3(x+6y)+4=9y+19