What does 90-12 mean?

Answer 1

102

Answer 2

Reading it out it says "ninety minus twelve" which means "90 take away 12". That's 78. Some people find that a bit hard to do so you could do it in two stages, take away 10 to get 80 then take away another 2 to get 78.

On the other hand, sometimes the "-" sign can mean "between", so in this case it would mean a number between 90 and 12, although in that usage the smaller number is usually written first.