so you would add $129 to $20 then you add p to the $20 because it doesnt say how many pairs he sold so we need to add an exponent. But then you need to put all that into and equation whihc leads you to get the answer of
1 + sec^2(x)sin^2(x) = sec^2(x) This becomes 1+tan^2(x) = sec^2(x) which is an identity You could 1 + sin^2(x)/cos^2(x) = sec^2(x) then cos^2(x) + sin^2(x) = cos^2(x)sec^2(x) 1 = 1