If y varies directly with x, means that they can be modeled by a linear equation, lets choose a line with 0 y intercept, that is:
y = mx + b
y = mx
where m is the slope of the line, now we plug in the data we have:
y = mx
20/3 = m(30)
solving for m:
m = (20/3)(1/30)
m = 20/90
m = 2/9
so the line equation, or function modeling the y and x relationship is:
y = (2/9)x
45 Cards
12 friends invited; 1/2 came 12 x 1/2=6
Let x stand for the number of cards each friend received
Armando kept 3
6x = 45-3
6x = 42
__ __
6 6
x = 7
Each friend received 7 cards
The solution to the problem is x < 31/55
okay idk if im right but...i think...units of measure means means like are feet,miles,kilomoters,cenimeters.
i think...hope this helps,theres a good chance im wrong