There are 10 sailboats in the harbor. Some of the boats have 2 sail & some of boats have 3 sails. If there are 24 sails visible on all of the boats, how many boats have 3 sails & how many boats have 2 sails?
Set it up like this;
2x + 3y = 24
x + y = 10 <--use this one to solve for y.
so y = -x + 10 ...
Now substitute (-x + 10) for y in the first equation..so
2x + 3(-x + 10) = 24
2x + (-3x) + 30 = 24
-x + 30 = 24
-x = 24-30 or -6
x = 6, y = 4
so 6 have 2 sails and 4 have 3 sails...