In Ellen's math class, there are 2 boys for every 3 girls. If there are 21 girls in the class, how many boys are in the class?

Haruka hiked several kilometers in the morning. she hiked only 66 kilometers in the afternoon, which was 25% less than she had hiked in the morning. how many kilometers did haruka hike in all?

Is triangle jkl congruent to triangle rst? if so, what is the scale factor?

Gabrielle's age is two times mikhail's age. the sum of their ages is 84. what is mikhail's age?