I'm not completely sure about this one, but I've got an answer :P b4=12 first you have to leave b by itself, so the positive 4 becomes negative as it switches sides. b=12-4 subtract 12 and 4 from each other b=8 the variable 'b' is 8 You need to find b13, and in order to find that you need to plug in the 8 where the b is (8)13 in the next step you have to multiply both 8 and 13 8(13)=104 Hope this helps