To do this, you need to first eliminate one variable. For sake of simplicity, I will eliminate y
4(5x+3y=17) + 3(7x-4y=32)
20x+12y=68 + 21x-12y=96
41x=164
x=4
Knowing x=4, we are able to plug this into one of the two initial functions.
5(4)+3y=17
20+3y=17
3y=-3
y=-1