Express the repeating decimal 0.73 as a geometric series and find its sum

0.737373...=0.73+0.73(0.01)+0.73(0.01)²+0.73(0.01)³...



The sum is 73/99.

We start out with
0.737373... = 0.73 + 0.0073 + 0.000073 + 0.00000073 + ...

This is the same as
0.737373... = 0.73 + 0.73(0.01) + 0.73(0.0001) + 0.73(0.000001) + ...

Which is the same as
0.737373... = 0.73 + 0.73(0.01) + 0.73(0.01)² + 0.73(0.01)³ + ...

The term number, n, relates to the exponent; when n = 2, the exponent is 1; when n = 3, the exponent is 2; etc.  This means the exponent is represented by n-1 in our series.

To find the sum, we see first that it is convergent because r = 0.01 < 1.  We can find the sum using 
a/(1-r), where a is the first term, 0.73:
0.73/(1-0.01) = 0.73/0.99 = 73/99

For number ten, you just need to write ANYTHING literally ANYTHING be it multiplication, division, addition, subtraction, but make sure they are in a parenthesis and you multiply by 0 outside the parenthesis.
example: 0(3+2346)
why? well because anything multiplied by 0 is equal to 0 

11. just substitute X3
8(1)+ 3(6)
8+18=26

12 2+w maybe i don't really know about this one it's been years lol

13. same as ten, but try substituting w for another variable or number, or try changing the 6 for another number, remember it can be ANYTHING as long as you multiply by zero OUTSIDE the parenthesis.

sorry that i wasn't able to help you at all on number 12.