Question 641332
Let x=the number
Now we are told that:
5x+10=2x-5   subtract 5x from and add 5 to each side
5x-5x+10+5=2x-5x-5+5 collect like terms
15=-3x  divide each side by -3
-5=x or
x=-5 the certain number
CK
5*(-5)+10=2*(-5)-5
-25+10=-10-5
-15=-15

Hope this helps---ptaylor