Add 18 each time
first term is -108
an=a1+d(n-1)
d=common difference
a1=startng term
an=-108+18(n-1)
31 term
a31=-108+18(31-1)
a31=-108+18(30)
a31=-108+540
a31=432
31st term is 432
Answer:
yes that is the correct answer
There are 431 females
785-77=708
708/2=354
354=males
354+77=431
431=females
to check work do 431=354 and that equals 785
Let's say that ground level is 0. When she goes down to the basement, she is going -12 feet since each flight of stairs is12 feet. Then she goes up 12 more feet= -12+12=0. She is back at ground level. Then she goes up another 12 feet= 0+12= 12. So I believe the answer is 12 feet.
