For a parallel circuit, the total resistance is called the equivalent resistance. The following equation is used to solve for it.

1/Req = 1/R1 + 1/R2 + 1/R3

1/Req = 1/10 + 1/22 + 1/100

To solve this problem, multiply both sides by the product of all of the denominators.

22,000 = 2,200 Req + 1,000 Req + 220 Req

3,420 * Req = 22,000

Req = 22,000 ÷ 3,420

This rounds to 6.43 Ω. I would not suggest that you round numbers before you have the answer. 1/22 is a repeating decimal.