480700. The different combinations of students that could go on the trip with a total of 25 student, but only 18 may go, is 480700.
The key to solve this problem is using the combination formula 
. This mean the number of ways to choose a sample of r elements from a set of n distinct objects where order does not matter and replacements are not allowed.
The total of students is n and the only that 18 students may go is r:
Dy/dx=1/2, 1/2, 1/2 etc
So this is a linear equation of the form y=mx+b where m=dy/dx=1/2 so
y=x/2 +b, now we can use any point to solve for the y-intercept, "b", I'll use (7,0)
0=7/2 +b
b=-7/2 so
y=x/2-7/2
y=(x-7)/2
Answer:
I believe the answer is -28
Step-by-step explanation
I gotchu bro
The answer is -28 because Liana starts at 25 below sea level (which is the same thing as -25) If she rises 9 feet, then you know to add because she is going up so your just gonna add. Next she descends 12 feet, so she went down, so subtract. So i know the answer is going to be -28 because -25+9 is -16, then imma subtract -16 and 12 so, -16 - 12= -28. There ye go
