Question 1207639


 {{{75+72+69+66}}}+.....+{{{21+18+15}}}

pattern:
common difference is {{{3}}}

1st term: {{{75}}}
2nd term: {{{75-3=72}}}
3rd term: {{{72-3=69}}}
4th term: {{{69-3=66}}}
5th term: {{{66-3=63}}}
6th term: {{{63-3=60}}}
7th term: {{{60-3=57}}}

and so on

{{{75+72+69+66+63+60+57+54+51+48+45+42+39+36+33+30+27+24+21+18+15}}}