Question

1. Jasmine is 5 years younger than twice her sister's age. If Jasmine is 39 years old, how old is her sister?

Answer 1

Let J be Jasmine age and S the sister's age. Then, we have

`2S-5=J`

this equality means Jasmine is 5 years younger than twice her sister's age. Now, we also know that J=39 years then by substituying this value into the last equality, we have

`2S-5=39`

and now, we can solve this equation for S. First, we must move -5 to the right hand side as 5. It reads

`\begin{gathered} 2S=39+5 \\ 2S=44 \end{gathered}`

and finally, we obtain

`\begin{gathered} S=(44)/(2) \\ S=22 \end{gathered}`

therefore, Jasmine's sister has 22 years old.