Complementary & supplementary (write out the equation and solve) help

At a sale this week, a desk is being sold for $213. this is a 29% discount from the original price. what is the original price?

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).

Maria found the least common multiple of 6 and 15. her work is shown below. multiples of 6: 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, . . multiples of 15: 15, 30, 45, 60, . . the least common multiple is 60. what is maria's error?