There are many different ways to figure this out but may I ask you one question....do you know whether the two legs are congruent or just the right angle?
If she buys one extra page she can put eight more photos. if she buys two extra pages she can put 16 photos. if she buys 3 extra pages she can put 24 more photos. if she buys 4 extra pages she can put 32 more photos
I believe the answer would be x20. Between the two parentheses there's a multiplication symbol. So you would just pretend that the parentheses aren't there cause the variable(s) (x) is/are like terms. So you would just multiply 10 times 2 and put out the x back in front of it