How do i work out?
2q+16=3p
q=-p+2

Use Substitution. 
2(-p+2)+16=3p
-2p+4+16=3pcombine like terms (4+16=20)
-2p+20=3padd 2pon both sides.
20=5pdivide by 5 each side to get p by itself.
p=4

q=-4+2substitute p in the equation  q=-p+2 as 4
q=-2

-2=-4+2Now I substitute the -2 and the 4 then add the negative because
                          it's a negative p. And they are equal!! :)