Which is the fraction for 0.21?

Arandom high school question but a hard one

Jim makes $10.35 per hour. write an equation that jim can use to calculate his pay.

Jack has a piece of red ribbon that is two times as long as his piece of blue ribbon. he says that he can use two different equation to find out how long his piece of red ribbon is compared to his piece of blue ribbon is. is he correct? explain his reasoning