Can anyone help me choose the correct answer?!

An advertising firm has an old computer that can prepare a whole mailing in 6 hours. with the of newer model the job is complete in 2 hours. how long would it take the newer model to do the job alone?

Jacob signs up to work for 2 1/2 hours at the school carnival. if each work shift is 3/4 hour, how many shifts will jacob work? (i just want to double check : |, for anybody that responds! : )

In priyas math class there are 10 boys and 15 girls. what is the ratio of boys to girls in priyas math class? express your answer as a decimal