How do you work out what x and y are equal to using x squared plus y squared equals 25 and y equals 3x plus 1?

since y = 3x+1 we have

y squared =(3x+1) squared

x^2 + y^2 = 25

x^2 + (3x+1)^2=25

x^2 + 9x^2+ 6x+1 = 25

10x^2 + 6x + 1 = 25

10x^2 + 6x -24 = 0

solve x from quadratic formula

x = 1.28

y = 3x + 1 = 4.83