Can anybody tell me the answer

42 tuna sandwiches, half on white, so 21 on white.  Leaves 21 on brown.

25% of 32 ham sandwiches on brown, so 8 ham on brown.  Leaves 24 ham on white.

20 more white than brown  total,

w = b + 20

w + b = 100

Adding

2w = 120

w = 60

b = 40

Cheese on brown = 40 - 21 - 8 = 11

cheese on white = 60 - 21 - 24 = 15

      T   C   H  Tot

B     21  11   8  40  

W    21  15 24 60