516.36 because the thousandth digit isn't above 5 so you don't round up
We are given that there are a total of 78 students. If we set the following variables:

Then, the sum of all of these must be 78, that is:

Since there are 15 in chemistry and physics and 47 in chemistry, we may replace that into the equation and we get:

Simplifying:

Now we solve for P by subtracting 62 on both sides:

Therefore, there are 16 students in physics
1. Is 8 seconds
2. I think is 15 quartz sorry if I’m wrong
The sine has a range -1 to +1 so y goes from 1+2(-1) to 1+2(1) = -1 to 3
Range: -1 ≤ y ≤ 3