Help me by showing me the step

Answer:
1. 15
Step-by-step explanation:
I'll help you out with question #1 and follow these steps to help you with solving the rest of the problems.
1. [tex]\frac{6-x}{3} = y[/tex] and we know that [tex]y=-3[/tex].
We can substitute [tex]y=-3[/tex] to the first equation.
[tex]\frac{6-x}{3} = -3[/tex]
Multiply both sides by 3 to get rid of the fraction.
[tex]6-x = -9[/tex]
Now you can solve for [tex]x[/tex], for which the value is 15.