What is 8 21/40 in decimal form? and need work

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

F(x) = 2x + 1? h(x) = x – h(x) = x + h(x) = x – 2 h(x) = x + 2

Cesar bought 7 items at the candy store. he bought candy bars for $0.50 each and packs of gum for $0.95 each. he spent a total of $6.80. what system represents the solution for the number of candy bars (x) and the number of pack gum (y) purchased?