One hundred times the quantity seven plus two I have to write the expression and then figure it out

"seven" means ' 7 ' "two" means ' 2 ' "the quantity seven plus two" means  ' (7 + 2) ' "one hundred times the quantity ..." means  ' 100 (7 + 2) '  That's the expression. One of the rules for handling these things is that you should always take care of anything inside parentheses first.  So do that.          (7 + 2)  =  9 Now you can can write the expression like this:    ' 100 (9) ' . That's just  900 .