How to find out how much you pay if there was a sale tax?

It is only 1 and 2 that is the solution to the differential equation

Step-by-step explanation:

1. x''=- 2 Cos t+ 3 sin t and x=2 cos t -3 sin t the addition give 0

2. d^2y/dx^2=- Sin x +2 and y =Sin x +x^2 the addition =x^2+2

but

3. dx/dt= -2 Sin 2t and tx =t Cos 2t =t( 2Cos t - 2 Sin t) the addition it can't equal Sin 2t