...............(eq1)
.............(eq2)
Rearrange eq2 to make q the subject:
Spoiler:
.........................(eq 2.1)
Sub the RHS of (eq 2.1) wherever q appears in (eq1):
Sub the value of p into (eq2):
Test these values
. This is correct
. This is correct
Your equation now shows
so you should be able to find by direct substitution.
Spoiler: