Identities

http://i144.photobucket.com/albums/r199/hei156/43.jpg

Let $y be Jerry's weekly wage before the increase.
Then, Tom's weekly wage before the increase = $10y.

10y(1 + 5%) - y(1 + 10%) = 8460
10y(1.05) - y(1.1) = 8460
10.5y - 1.1y = 8460
9.4y = 8460
y = 900
10y = 9000

Before the increase,
Jerry's weekly wage is $900, and Tom's weekly wage is $9000.


http://i144.photobucket.com/albums/r199/hei156/61.jpg

An obtuse is greater than 90o but smaller than 180o.
90 < 4x + 30 < 180
90 - 30 < 4x < 180 - 30
60 < 4x < 150
60/4 < x < 150/4
15 < x < 37.5
=