Answer: The lowest grade that Lisa can get in her last test is 94.
Step-by-step explanation: Given that Lisa’s test grades are 79, 89, and 90 and there will be one more test this year.
We are to find the lowest grade Lisa can get on her last test if she wants her test average to be at least 88.
Let x represents the grade that Lisa get in her last test.
Then, according to the given information, we have

Thus, the lowest grade that Lisa can get in her last test is 94.