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
Answer:
T C H Tot
B 21 11 8 40
W 21 15 24 60