Debra earns $7.50 an hour, plus tips, as a waitress. suppose she works 24 hours in one week. how much money must she receive in tips to earm more than $250 that week? .

The total amount of money Debra earns is the sum of her wage and the tip. Since she earns $7.50 per hour and she worked for 24 hours, her weekly wage is 180. Suppose we let x be the amount of tip, her total earnings is 180 + x. This amount should be more than $250. 
                                       180 + x > 250
                                             x > 70
Thus, Debra should receive more than $70 tip. 

Let x = Debra's earnings in a week; y = tips as waitress

x+y > 250
24*7.50 + y > 250
180 + y > 250
y > 70.

She needs to receive tips more than 70 dollars to earn more than 250 dollars that week.

It is 5.8 you add all of the up to equat 180 then solve the equation