Step on how to calculate variance

An objects motion is described by the equation d= 4sin (pi t) what will the height of the object be at 1.75 seconds?

Which ordered pair is a solution to the system of linear equations? 2x + 3y= 6 –3x + 5y = 10

Add, subtract, multiply, or divide as indicated. list any restrictions for the variable(s) and simplify the answers when possible. 1) x-2 / x+5 + 3x / 2x-1 2) x+6 / x-6 - x^2 / x+6 3) x+9 / x-4 + x+2 / x^2-11x+28 4) x / x^2-64 + 11 / 2x^2+11x-40 5) 5 / x + 11 / x-3 - x-4 / x^2+2x-15