x * (1-60/100) = 0.4x 
0.4x + 60 = 240 
0.4x = 240 - 60 
0.4x = 180 
x = 180/0.4 
x = 450 
The starting number is 450 
What I did was decrease x “unknown starting number” by 10% giving 0.4x then I made a second equation by adding 60 and equaling to 240 then I simplified to find x. 
ANSWER 
Original “starting number” = 450