In problems 7 12, rewrite each summation using the sigma notation. Do not evaluate the sums. 7. 3+4+5+...493+94 8. 4+6+8+...+24 9. 9416+25+36+...+ 144 3 3 3 3 1 2 3 7 10.7+5+T6 +---+700 11, 127 +22 4327 + .. . +72 12. 3+6+9+...+30