Lets make wirebound = x

Lets make college rule = y

x + y = 50 [an undefined amount of wirebound and college ruled notebook is 50 notebooks]

.76x + 3.68y = 128.52 [ $.76 per wirebound and $3.68 per college ruled came out to be $128.52]

Lets solve the first equation for x.

x + y = 50 --> x = 50 - y [Subtract y from both sides]

Plug that equation into the variable for x into the second equation.

.76x + 3.68y = 128.52 --> .76(50 - y) + 3.68y = 128.52

38 - .76y + 3.68y = 128.52

2.92y = 90.52 [Simplify the y terms, and subtract 38 from both sides]

y = 31 [Divide both sides by 2.91]

Now we know y is 31, we plug that back into the first equation to get,

x + y = 50

x + 31 = 50

x = 19 [Subtract both sides by 31]

The university bookstore sold 19 wirebound graph-paper notebooks and 31 college-ruled notebooks.

You may check your work by plugging the values of x and y back into the two equations, and it should come out right.

Please put me A + rating