Answer:
10 minutes
Step-by-step explanation:
Let's use the variable x for the amount of coins.
The first machine can sort x coins in 15 minutes, so its speed is x/15 coins/minute.
The second machine can sort x coins in 30 minutes, so its speed is x/30 coins/minute.
If we sum the speeds, we have that the speed will be:
speed = (x/15) + (x/30) = (2x + x)/30 = 3x/30 = x/10
The total speed can sort x/10 coins per minute, that is x coins in 10 minutes.
Oh for sure, true true true! A good example would be a workout routine, find out what best works.
It's a linear function. We need only two points to draw a graph.
We choose any values of x and calculate the value of y.

for x= 0 → y = 3(0) - 1 = 0 - 1 = -1 → (0, -1)
for x = 2 → y = 3(2) - 1 = 6 - 1 = 5 → (2, 5)

for x = 0 → y = 3(0) - 1/3 = 0 - 1/3 = -1/3 → (0, -1/3)
for x = 2 → y = 3(2) - 1/3 = 6 - 1/3 = 5 2/3 → (2, 5 2/3)
Consecutive interior theorem
X+96+96+x= 180
2x+192=180
2x= -12
X=-6
C= 50y+20x
Where y is the number of boxes holding 50 pieces each and x is the number of boxes holding 20 pieces each.