Question 210199
Let x = grade of last quiz



Remember, the average of 5 numbers is simply the sum of those 5 numbers divided by 5. In other words, the average of 73,75,89,91, and 'x' (the last quiz score) is {{{(73+75+89+91+x)/5}}}



Since you want "at least 85", this means that the average has to be greater than or equal to 85 like so



{{{(73+75+89+91+x)/5>=85}}}



I'll let you take it from here. Let me know if you need more help.