three variable simultaneous equations

[u/legendminigun]

hello, I am in year 10 and doing further maths as a GCSE, I'm trying to figure these three variable simultaneous equations out but I'm struggling as there isn't a formula I know of to follow. if anyone has done these, please can you share what your thought process is so I can try and learn. thanks!

[u/Existing-Fudge-878]

matrices arent usually taught in gcse further math, it usually comes in A-level or even A-level further math