1800 can be factored into 60*10*3
Since I see a 60 and a 5c, I am going to set them equal to each other and solve for c, which would give me a 12; since 5*12 is 60.
Now I see a 3 and a 3b. I would set them equal to each other gain and solve for them. b is equal to 1; since 381 is 3.
Lastly, I see a 10 and 2a. I would set them equal to each other and solve for them. a would be equal to 5 since 2*5 is 10.
when we multiply all the numbers, we would get 1800, since 2*5*3*1*12*5 would be equal to 1800.
So, a = 5, b = 1, and c = 12.
The question asked for C, it is equal to 12.
HOPE THIS HELPS!