You can plug in each point into both equations to find your answer, or you can do substitution:
y = 3x - 10
2x + 3y = 3
Plug in the first equation into the second equation:
2x + 3y = 3
2x + 3(3x - 10) = 3 [since y = 3x - 10, you can substitute (3x - 10) for y]
Multiply/distribute 3 into (3x - 10)
2x + 9x - 30 = 3
11x - 30 = 3 Add 30 on both sides
11x = 33 Divide 11 on both sides
x = 3
Now that you know x, you can plug it into one of the equations to find y
y = 3x - 10
y = 3(3) - 10
y = 9 - 10
y = -1
(3, -1)
[proof]
y = 3x - 10
-1 = 3(3) - 10
-1 = 9 - 10
-1 = -1
2x + 3y = 3
2(3) + 3(-1) = 3
6 - 3 = 3
3 = 3