27) B

The first thing we need to find out is how many tokens does it take to get a free meal.

Since Tim receives 7 tokens every day, the cost of a free meal must definitely be more than 7 tokens otherwise he would never run out.

If the cost of a free meal is 8, then the net number of tokens lost each day = 8 – 7 = 1
If the cost of a free meal is 9, then the net number of tokens lost each day = 9 – 7 = 2

Since Tim had 20 tokens on Monday 1st and the cost of each meal is 8, he would have had 12 tokens by next Tuesday which means he would have had enough for a meal. However, this is not the case as he did not have enough tokens to get a meal on Tuesday.

If the cost of a meal was 9 tokens, he would have had 8 tokens left. This would not be enough for him to buy a meal. Hence cost of a free meal = 9 tokens.

On Wednesday next morning, he would have 8 + 7 = 15 tokens.
After free meal = 15 – 9 = 6 tokens

On Thursday morning, he would have 6 + 7 = 13 tokens.
After free meal = 13 – 9 = 4 tokens

On Friday morning, he would have 4 + 7 = 11 tokens.
After free meal = 11 – 9 = 2 tokens

On Monday morning, he would have 2 + 7 = 9 tokens.
After free meal = 9 – 9 = 0 tokens

On Tuesday morning, he would have 0 + 7 = 7 tokens.
Since he does not have 9 tokens, he would not be able to get a free meal.

Hence the next day of the week in which Tim cannot get a free meal is Tuesday.