+120 There are 3 times as many pens as erasers. The ratio of the number of erasers to the number of rulers is 3 : 2. There are 28 more pens than rulers. How many pens are there?
(1) 8
(2) 36
(3) 56
(4) 84
+129899 Let the number of pens = 3x
Let the number of erasers = x
Let the number of rulers = 3x - 28
And we know that
x / ( 3x - 28) = 3/2 cross-multiply
2x = 3(3x - 28) simplify
2x = 9x - 84 rearrange
9x - 2x = 84
7x = 84
x = 84 / 7 = 12 = number of erasers
Number of pens = 3x = 3(12) = 36
