Joanna went school supply shopping. She spent $30.70 on notebooks and pencils. Notebooks cost $2.20 each and pencils cost $1.09 each. She bought a total of 19 notebooks and pencils. How many of each did she buy?

Ok, so we need to set up a system of equations.

x + y = 19, where x is notebooks and y is pencils

2.2x + 1.09y = 30.70. You use the coefficient for individual prices and the total for the total given.

2.2x + 2.2y = 41.8 (multiply for elimination later)

2.2x + 1.09y = 30.7

1.11y = 11.1

y = 11.1/1.11

y = 10

Now we use the substitution method in x + y = 19

x + 10 = 19

x = 9

9 notebooks and 10 pencils