Answer:
90
Step-by-step explanation:
To find s4 we find sum of values when n=1,n=2,n=3,n=4
given expression is 
n=1 , plug in 1 for n

n=2

n=3

n=4

Sum of all 4 terms = 6+12+24+48=90
Answer:
Step-by-step explanation:
Explanation
6 sprinters are in a race. Any one of the 6 could win. None of them can win 2 medals. So the first result is 6
5 runners remain. The second medal goes to any one of the 5
4 runners remain after 1 of the 5 have been choosen. Any one of the 4 could win.
Answer 6 * 5 * 4 = 120
There are 120 ways of awarding 3 medals to 6 people.
Parentheses are used to identify which numbers you should add,multiply .ect first. So If i had
12-(3+1)=x
then you would want to solve 3+1 before you subtract 12.
Answer:
y = 3
Step-by-step explanation:
(5y - 3)/4 + 6 = 3y
5y - 3 + 24 = 12y
7y = 21
y = 3
Check.
(5*3 - 3)/4 + 6 = 3*3
(15 - 3)/4 + 6 = 9
12/4 + 6 = 9
3 + 6 = 9
9 = 9
10 x 30=300 because you 3 tens is 30 times 10 is 300. hope it helped.