if the sixth term of an Ap is 37.5 and the 17th term is -100 find the 10 term and 15 term sum of the first 10 term

please help me

a+5d = 37.5
a+16d = -100
subtract to get
11d = -137.5
d = 12.5
so a = -25
Now just use
a_n = a+(n-1)d
Sn = n2 (2a+(n-1)d)