Question

Please help me with this probability question, I’ve got my maths exam tomorrow (13th June)

Answer 1

$\dfrac{2}{n-1}=\dfrac{3}{n}-0.1\\2n=3(n-1)-0.1n(n-1)\\2n=3n-3-0.1n^2+0.1n\\0.1n^2-1.1n+3=0\\n^2-11n+30=0\\n^2-5n-6n+30=0\\n(n-5)-6(n-5)=0\\(n-6)(n-5)=0\\n=6 \vee n=5$