Lets get started :)
y = 3x + 30
y = 8x
Since y = both the equations, we can equate them
8x = 3x + 30 {Take 3x by subtracting to the other side in order to find the value of the variable)
We do minus, when we see plus
8x - 3x = 3x - 3x + 30
3x and -3x cancels out in the right hand side
5x = 30
Divide by 5 on either side to isolate x
We do division, when we see multiplication

5 and 5 cancels out
x = 6
Now, we need to substitute x by 6 in order to find y
We can substitute in either equation, we will still get the same value
y = 8(6)
= 48
y = 3(6) + 30
= 18 + 30
= 48
x = 6 , y = 48