A truck delivered *n* number of boxes weighing 20 pounds and *t* number of boxes weighing 30 pounds to a warehouse. The equation *w* = 20*n* + 30*t *can be used to determine the total weight *w*, in pounds, of the boxes. If the total weight of the boxes delivered was 480 pounds and 12 boxes weighed 30 pounds, how many boxes weighed 20 pounds?

**Maps to Category 15 of the book.**

**Answer posted on 08/01/2021: Answer is 6.**

*w* = total weight of boxes* *is given as 480.

*t = *number of 30 pound boxes is given as 12*.*

Plug the above values in the equation to determine the number of 20 pound boxes = *n.*

*w* = 20*n* + 30*t --> *480 = 20*n *+ (30 x 12) --> 480 = 20*n* + 360 --> 20*n* = 120 --> *n* = 6

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