Let the number be 10x+y
According to question, we have,
10x+y=5(x+y)
=>10x+y=5x+5y
=>5x=4y
Also, 10x+y−2xy=5
=>10x+45x−2x×45x=5
=>10x+45x−410x2=5
=>40x+5x−10x2=20
=>10x2−45x+20=0
=>2x2−9x+4=0
=>2x2−8x−x+4=0
=>2x(x−4)−1(x−4)=0
=>(2x−1)(x−4)=0
=>x=4
y=45x=45×4=5
Required number is 10×4+5=45