I'm pretty sure its 5, because theres 15 on the one side and 10 on the other and the <em><u>?</u></em><em><u> </u></em> side would be 5 then.
The quadratic formula is
and in the equation ax^2+bx+c=0
so now all you have to do is substitute the numbers into the quadratic formula
Liza is wrong because...
Friday = 237
Saturday = 237 + 446
Both days = 920