Using “:=” to define a function of your own, and then using that function:

f[x_,y_] := x^2 * y^3

f[3,2]

Solving an equation with “Solve.” Notice that the equation can involve your own functions as well as ones built in to Mathematica.

Solve[ f[x,2] == 72, x ]

To solve a system of equations for values of more than one variable, list the equations of the system in curly braces, and the variables you want to solve for inside another pair.

Solve[ {x + y == 2, x - y == 1}, {x,y}]