On a math test, 60% of the students used a pencil. Half of the remaining students used a red pen. If 6 students used a rend pen, how many students are in the class?

60% used a pencil ... that leaves 40% remaining students (100% - 60% = 40%)

half of those used a red pen ... so 20% used a red pen. (40% / 2 = 20%)

6 students used a red pen. so ... 6 students is 20% of what number?

6 = 0.20x

6/0.20 = x

30 = x

There are 30 students in the class