4250 yellow and white tennis balls will be used 3/5 of the tennis balls are yellow. after the tournament the yellow balls are sold for £2.50 per can of three. 85% of the money from the sale of the tennis balls is given to charity. how much will the charity get?

What i understand is 3/5 of the balls are yellow and all of these will be sold as 3 per can.

If so,

3/5 of 4250 tennis balls is 2550 (4250*3/5=2550)
These are yellow tennis balls.

If you pack as 3 of these balls, you get 850 cans. (2550/3 =850)

And if you sell these as £2.50 per each, 850*£2.5=£2125

85% of this money goes to charity;
£2125 * 85/100 = £1806.25

A=bxh3.2x1.8=5.76 centimeters square