Let the second number be x
[tex] (x+5)^{2}-5x=2[(x-5)x]+25 [/tex]
[tex] x^{2} +10x+25-5x=2[ x^{2} -5x]+25[/tex]
[tex] x^{2} +5x+25=2 x^{2} -10x+25[/tex]
[tex] x^{2} +5x=2 x^{2} -10x[/tex]
[tex]5x= x^{2} -10x[/tex]
[tex]15x= x^{2} [/tex]
[tex]15=x[/tex]
Therefore the three multiples of 5 are 10, 15 and 20