Toshi is 7 years older than his brother Kosuke, who is twice as old as

This is a very easy question on Word problems, specifically related to ages. This is also a good question for you to understand the basics of framing equations. In case this is an area that you currently face issues with, try solving more problems of this type.

The first step in developing an equation is to develop the variables. Variables are values which represent the unknowns in the question.
The second step is to connect the variables using mathematical operators and develop the LHS and RHS of the equations.
Once you have the LHS and the RHS, you have the equation.

Remember that, most often, the issue that you face with word problems is about framing the equations and not actually solving them. So, once you have the equation in place, solving it won’t be that much of an issue.

In this question, there are 3 unknowns - the ages of Toshi, Kosuke and Junko. Therefore, let’s use 3 variables – T, K and J to represent them.

Toshi is 7 years older than Kosuke. This means, age of Toshi is 7 years MORE than age of Kosuke. So,
T = K + 7. Let this be equation 1.

Kosuke is twice as old as Junko. This means, age of Kosuke is double/two times of age of Junko. So,
K = 2J. Let this be equation 2.
But, age of Junko is 8 years. So, J = 8.

Substituting this value in equation 2, we get K = 2*8 = 16.

Substituting the value of K in equation 1, we get T = 16 + 7 = 23.

Toshi is 23 years old. The correct answer option is D.

Hope this helps!