Before the advance-purchase deadline, the cost of attending a particular event is $90. after that, the price goes up to $117. what is the percent of increase in the cost of the event?

The percent increase in the advance-purchase deadline is 30% because if you divide $90 by 10 you get 9 and multiply that by 3 and you will get an 30% increase

word problem: 90 ÷ 10=  9 x 13 =1 17

X^2 - y^2 - 2y - 1 A trick I learned, if there is a square with know number in front of the x etc, that means in each bracket there with be an x and as it is a positive x^2 means that both brackets will have positive x at start, so the same with y, except this is minus which means that either one doesn't matter can be a minus y and one positive as when you times a positive and negative you get a negative and for the one, you find two factors that go into one, which there is only one one and that is one which puts it at the end of the equation, but it is minus so like the y^2 one must be minus and one positive So (x + y + 1) (x - y - 1)