Ineed as soon as possible with the problem bellow
simplify each of the following with justifications for your
a. 290 mod 26
b. 9^{-1} mod 26
c. -15 mod 26

A)  290 mod 26

We subtract the largest multiple of 26 which is less than 290. The answer we get after the subtraction is the answer.

Largest multiple of 26 is 286, because 26 * 11 = 286

290 - 286 = 4.

290 mod 26 = 4.

b). 9^(-1)   mod 26 =   0.111  mod 26.

 0 * 26 = 0.
The largest multiple of 26 which is less than 0.111 is 0.
We subtract this from 0.111

0.111 -  0 = 0.111

9^(-1)   mod 26 =  9^(-1)  = 0.111

c). -15 mod 26.

Take note this is negative numbers. But same rules applies here.

The largest multiple of 26 which is less than -15 is -26.

We subtract this from -15

-15 - (-26) = -15 + 26 = 11

-15 mod 26 = 11