On a math test, twelve 8th graders averaged 80.00, while twenty 7th graders averaged 70.00. For all 32 students, the average was?

Remember that average = (sum of numbers) / n. So from the average, you can get the sum.

" twelve 8th graders averaged 80.00,"
So the total of their scores is 12 * 80

"while twenty 7th graders averaged 70.00."
So the total of their scores is 20*70

"For all 32 students, the average was"
The total of their scores, divided by 32.

75.00.

Learned this ages ago in high school 🏫 - I was the first in my class though for some reason I can't remember how to work out averages
To my memory which isn't that great nowadays due to I've got a brain injury to concussions though I think it's got something to do with deviding