How do you solve this question algebraically?

y=x+5 if y=3x

Substitution ... sub in 3x for y in the other equation

y = x + 5

3x = x + 5

3x - x = 5

2x = 5

x = 5/2

now sub 5/2 in for x in either of the original equations to find y

y = 3x

y = 3 (5/2)

y = 15/2

solution is (5/2, 15/2)