Ok, so you are given the value of P=q+2
The substitution method tells us that we must insert the value we know, into the second equation, 4P+3q= -27
Doing so will give us 4(q+2)+3q= -27
For right now, lets just focus on the first part, 4(q+2)
We can simplify this by distributing(multiplying) the 4 to whats inside the variables.
This will give us 4q+8
now lets add this back to the rest of the equation >>> 4q+8+3q = -27
We can further simplify by adding like terms >>> 7q+8 = -27
subtract the 8 from both sides >>> 7q = -35
now divide both sides by 7 >>> q = -35/7
Therefor q = -5
EDIT*
now that we know q = -5 we can put q into the equation for P !
we know that p=q+2
so lets put q in now >>> p=(-5)+2
and simplify>>> p = -3
I hope this helps:)