i am lost after i add 79,56,91,72 i divide by 4 after this is were i am stuck can you help me out i learn better if i can see the steps just once. here is the problem:

A student has made a 79, 56, 91 and 72 on four tests. Determine the possible scores on the fifth test that will result in a 75 or higher average (assume an average cannot go higher than 100)…Hint: set up an inequality to calculate the grade if the average would be between 75 and 100.