billy is $\frac 15$ of his brother's age. in $9$ years, billy will be $\frac 12$ of his brother's age. what is the sum of their current ages, in years?

Ageologist had two rocks on a scale that weighed 4.6 kilograms together.rock a was 0.5 of the total weight.how much did rock a weigh?

The lengths of all sides of a triangle are integers when measured in decimeters. one of the sides has length of 1 dm and another of 3 dm. find the perimeter of the triangle.'

See attachment below and find the equivalent of tan(∠qsr)