Solve as simultaneous equations or substitute for the x or y value, and then get the other x or y value by substituting.
Substitution method:
y + 4x = -24
x = 3y - 45
Substitute the x into the first equation.
y + 4 (3y-45) = -24
Simplify and solve for y
y + 12y - 180 = -24
13y = -24 + 180
13y = 156
y = 12
Substitute y into one of the equations to find the x value.
x = 3(12) - 45
x = -9
(-9,12) is where the lines intersect.