On Friday a local hamburger shop sold a combination total of 420 hamburgers and cheeseburgers. the number cheeseburgers sold was three times the number of hamburger sold. how many hamburgers were sold on Friday?

105 hamburgers were sold.

Step-by-step explanation:

In order for the number of cheeseburgers to be 3 times the number of hamburgers, the hamburgers must be 1/4 of the total amount sold. 420/4 = 105. This leaves the number of cheeseburgers as 315. 105 x 3 = 315, which proves this is right.

15

step-by-step explanation:

we are given the following expression and we are to solve it and find the product:

-13 × (-5)

solving the given expression in the standard order of solving a mathematical expression, beginning with the opening of brackets and then multiplying the terms and changing their signs.

-3 × -5 = 15 (answer is positive because when negative is multiplied with negative, it gives a positive answer)

irrational, cannot