"Combinations" isn't really the right word, because a combination doesn't take order of elements into account, and the outcome of a race certainly does depend on order. "Permutations" would be the correct term.
If 4 students are competing, then the race has
4! = 4 • 3 • 2 • 1 = 24
possible outcomes.
5.85+2.50+1.95 x 2.5=13.225
Barbara spends $13.23. Hope I helped.
M1= 5 , M2=1
Explanation:
12-3m-4-5/m=0
8-3m-5/m=0
(8-3m-5/m=0) * m
8m-3m^2-5=0
8m-3m^2=5
m(8-3m)=5
m1=5
m2=> (8-3m)=5
3m=3
m2= 1
2x²-10xy+3xy-15y²
Add like terms.
2x²+ (-10xy+3xy) -15y²
Simplify.
2x² + (-7xy) - 15y²
Rearrange the equation.
2x²-15y²-7xy
~Hope I helped~
-10+(-30)+(-25)+10+15 is -40 divided by 5 to get the average because you find average by dividing the sum of all the numbers by how many there are is -8