Hello again guys,

I have five problems to solve but found myself stuck by this question other thought to be very simple but I am unfortunately not. Could you guys explain it how to solve this problem? I don't know how to make the base number the same because both a and b is variable and not number. Thank you very much for your help.

Solve the following simultaneous equations:

My first time using the Latex software, so please forgive me if I've made a mistake.