If holly, alex and ben had 100 balls. holly had 20 balls and alex had 2x as many as she did, how many did ben have?

Holly has 20 balls, and there are 100 balls in total.

So there are 100-20 = 80 balls left.

Alex had 2 * the amount Holly had, which is 20.

So Alex has 20 * 2 = 40 balls.

Together, they have 60 balls.

Which means 100-60 = 40. So Ben has 40 balls.

Check:

Holly: 20

Alex: 40

Ben: 40

Add them: 20 + 40 + 40 = 100

40 balls

Step-by-step explanation:

Let the number Ben has be A.

Holly, Alex and Ben had 100 balls.

Holly had 20

Alex had 2x holly = 2 x 20

= 40 balls

Therefore

20 + 40 + A = 100

60 + A = 100

Subtract 60 from both sides

60 - 60 + A = 100 - 60

A = 40

Ben had 40 balls

Check

Holly + Alex + ben

20 + 40 + 40

= 100 balls