What you do is you put three on top because a=3 and then you add 5 and 3 to get 8 for the bottom and you get a answer of 3/8 which you cannot simplify with whole numbers
8/x-7=7/2 16=7(x-7) cross multiply 16=7x-49 -7x=-49-16 -7x=-65 divides each side by -7 -7x/7=-65/7 X=65/7 Alternative form X=92/7 Which is 1st options in your questions.