NUMERICAL ABILITY: Algebraic Expression. Solve for the value of the remaining variable 

NUMERICAL ABILITY: Algebraic Expression.
Solve for the value of the remaining variable given the value of the other variables.
1.) P = 2L + 2W, when L = 3cm and P = 200cm
2.) I = PRT, when P = 25,000; I =1000; and T = 0.5 year
3.) S= D/T, when S = 360kph and D = 60 km
4.) x + y = 12, when y = 4
5.) xyz = 45, when x = 3 and y = 3
6.) -2x² + 4 when x = -1
7.) 5b - b² when b = 3
8.) (3+9x)/2 when x = -2
9.) (2w-4)/5 when w = -3
10.) 2x + 2y = 1 when x = 2