You need to find a number which either has 6 and 9 as factors or 8 and 5 as factors.
I will go with 18
9p + 8q = 2 —> to get to 18p you have to multiply 9 by 2 so multiply the whole equation by 2
6p - 5q= 26 —> to get to 18p you have to multiply 6 by 3 so multiply the whole equation by 3
You end up with:
18p + 16q = 4
And
18p -15q = 78
Since they both now have a common term (18p) you can subtract them from one another by elimination to have 1 unknown left in the equation.
18p + 16q = 4
- 18p - 5q = 78
Goes to 21q ( - and - is a +) = -74
So q=-74/21
When this is substituted in original equations (ideally the easier one)
9p = 2-8(-74/21)
You will obtain p through division by 9