Oleg, Sasha, and Dima shared 600 toys. Sasha had twice as many toys as Oleg. Dima had 40 more toys than Oleg.
Let the number of toys Oleg has = x
Let the number of toys Sasha has = y
Let the number of toys Dima has = z
Sasha had twice as many toys as Oleg
So y = 2*x= 2x
Dima had 40 more toys than Oleg.
z = x + 40
Oleg, Sasha, and Dima shared 600 toys
x + y + z= 600
We know y=2x and z=x+40
Replace it for y and z
Subtract 40 on both sides
Divide by 4 on both sides
Oleg had 140 toys