On a local newspaper yesterday, this question is reported to be controversial for primary school examination since it is too difficult. It goes like this. There are two people and the older one said:
“When I was at your age, you were only 5.
When you become as old as I am now, I will become 71.”
The question is, how old are these two people?
It turns out, according to the newspaper, the question is not aimed at simultaneous equation at all, but to solve the problem by graphically dividing lines in proportion.
To solve in an overkill fashion by Nspire:
And this is also a refresher on how to solve simultaneous equations on TI-84 series using the rref function (reduced row echelon form). Define the equations in form of matrix (as [A] below), and then run the rref() function on it. The result matrix contained the solution to the problem.
And just in case Excel is the only tool available, no worry, its solver will get you covered (!).