Does anyone know how to multiply polynomials

Tomas is making trail mix using granola and walnuts. he can spend a total of $12 on the ingredients. he buys 3 pounds of granola that costs $2.00 per pound. the walnuts cost $6 per pound. he uses the equation to represent the total cost, where x represents the number of pounds of granola and y represents the number of pounds of walnuts. he solves the equation for y, the number of pounds of walnuts he can buy. answer- b tomas added 6 to both sides of the equation instead of subtracting 6. just took the test

The graph represents the gallons of water in a water tank with respect to the number of hours since it was completely filled

Write an equation in point-slope form for the line through the given point that has the given slope (-2,-7); m=-3/2