Let: x = cost of the pepperoni pizza y = cost of the plain pizza
Next, set up equations based on the word problem. We then have the following equations:
(1) 3x + 2y = 58.50 (2) 2x + 4y = 67
Equation (1) comes from the statement: "Jack paid 58.50 for 3 pepperonies and 2 plain pizzas". Equation (2), on the other hand, translates the statement: "Jill paid 67 for 2 pepperonies and 4 plain pizzas".
To solve for two unknown variables given two independent equations, eliminate one variable first. That is, multiply equation (1) to -2.
The place value of the 5 in 6.85 is in the thousandths place. The 8 would be the tenths place. Other than that I'm not quite sure what the question is asking.