Answer :
[tex]30*0.4=12 \\ \\ 30-12=18[/tex]
Since 12 is 40% of 30, she has already completed 12 problems. Subtract that from 30, and you can find that she still needs to do 18 problems.
Using Proportions:
[tex] \frac{40}{100} = \frac{x}{30} \\ \\ 100x=1200 \\ \\ x=12 \\ \\ 30-12=18[/tex]
Since 12 is 40% of 30, she has already completed 12 problems. Subtract that from 30, and you can find that she still needs to do 18 problems.
Using Proportions:
[tex] \frac{40}{100} = \frac{x}{30} \\ \\ 100x=1200 \\ \\ x=12 \\ \\ 30-12=18[/tex]
