Well instead of guess and checking, you can simply do 88 x 66. But whatever you do to the bottom you MUST do to the top.
STEP 2
since 88 x 66 = 5808
and the equation was 2/88 + 2/66, Since 88 multiplys 66 to give 5808, you must multiply the numerator (the top) by 66 as well, so 2/88 becomes 132/5808
Try do the same for the other one.
2/66 --> 176/5808 (because the denominater 66 needs to multiply by 88 to get 5808)
STEP 3
Add the two
Now after multiplying, you now have
132/5808 + 176/5808,
Since the denominator is the same we can add the top