What you need to do is find the smallest multiple that they both have (i forgot what that is called) list them like this:
12: 24 36 48 60 72
15: 30 45 60 75
60 is the lowest number that they both can multiply to
60 cups/lids is the answer
(-3) + (-5) + 9
(-3) + (-5) = -8
-8 + 9
= 1
The volume formula is V= l x L x H, l=width, L=Length, H= Depth, so
2x3 _ 9x2 + 7x + 6 = l x L x (2x + 1), because H=(2x + 1), so
l x L= (2x3 _ 9x2 + 7x + 6 )/ (2x + 1) = (2x3 _ 9x2 + 7x + 6 ) X [1/(2x + 1)]
case1: l= (2x3 _ 9x2 + 7x + 6 ) or L= 1/(2x + 1), case2: L= (2x3 _ 9x2 + 7x + 6 ) or l= 1/(2x + 1)
the why question:
perhaps there is similarity of value between volume and l, or volume and L
Assuming n is the number of signers.
7 is 10% of y.
7 = 0.1y
y = 70
n is 80% of y
n = 0.8y
n = 0.8(70)
n = 56
56 signers
These how many that are left there are 27 pens