Answer
Pens cost 20 cents each, while tablets cost 80 cents each.
Work Step by Step
We set up a system of equations:
$7t+4p = 6.40$
and
$2t+19p = 5.40$
We now substitute the second equation into the first:
$7( \frac{5.40-19p}{2})+4p = 6.40$
Now, we use PEMDAS, a method for simplification. This acronym reminds us that we must first address parentheses, and then exponents. Next, we address multiplication and division, going from left to right. Lastly, we simplify addition and subtraction from left to right. This gives:
$ p = .20$
We substitute back into the first equation and solve for the price of tablets. When we do this, we find:
$t = .80 $