You have the following system of equations:
x + 3y = 1
y = 2x + 5
in order to solve the previous system, replace the expression y = 2x + 5, into the first equation and solve for x, as follow:
x + 3y = 1
x + 3(2x + 5) = 1 apply distribution property
x + 6x + 15 = 1 simplify lef side
7x + 15 = 1 subtrac 15 both sides
7x = 1 - 15
7x = -14 divide by 2 both sides
x = -14/2
x = -7
replace the previous value of x into the second equation to get y:
y = 2x + 5
y = 2(-7) + 5
y = -14 + 5
y = -9
Hence, the solution to the given system of equations is:
x = -7
y = -9
(-7 , -9)