To solve this equation there are many ways you can do to solve. One way is to simply substitute one variable for another.
5x = 5y - 25
X = y - 5
10y = 42 + 2x
10y = 42 + 2(y - 5)
10 y = 42 + 2y - 10
8y = 32
Y = 4.
X = y - 5
X = 4 - 5
X = -1.
P(X,y) = P(-1,4). This would be the solution or the point where they would intersect.