Answer
The 7th class: 550-500.
Work Step by Step
The difference between the heights of two consecutive classes, that is the upper limit of the class and the upper limit of the previous class, gives us the relative frequency of the class.
The upper limit of the 5th class: $\approx0.30$
The upper limit of the 6th class: $\approx0.45$
The upper limit of the 7th class: $\approx0.61$
The relative frequency of the 6th class: $0.45-0.3=0.15$
The relative frequency of the 7th class: $0.61-0.45=0.16$
Notice that the given values are an approximation. Visually, they look the same.
