For this, you've got to double one of the equations, and this will then allow you to eliminate part of the equation.\(2x+5y= 145 \\ 2x+2y=100.
\\ 5y-2y= 145-100 \\ 3y=45 \\ y=15\)
As you've now got one part, you've got to substitute this in, and this gives you;
\(2x+5*15= 145 \\ 5*15=75 \\ 145-75= 70 \\ 2x=70 \\ x=35\)
\(x+1*15=50 \\ 50-15= 35 \\ x=35\)
Once you've done both equations, you have to ensure that they're correct, and in this case, they are.
Therefore, \(y=15 \\ x=35\)
Hope this helps :)
