Help solving this simultaneous equation?

It is 2r-s=10
rs-s² =12

Could you show the workings please?

2r-s= 10 or s = 2r-10
substituting in rs - s² = 12,
r(2r-10) - (2r-10)² = 12
collect terms & simplify
r² -15r +56 = 0
(r-7)(r-8) = 0 , ie r = 7 or 8 substitute to get
ans: (7,4) , (8,6)
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