Problem 1:

Because Leon uses 300g of mixture, the number of ml of water needs is: 30*3 = 90 ( ml )

So Leon needs 90ml more water.

Problem 2:

Total number of bananas Jacob has: 3*60 = 180 ( bananas )

Number of bananas he gave to the class: 180 - 28 = 152 ( bananas )

So Jacob has 152 bananas left.

Problem 3:

Total amount for both two and three games: 2*3*75 = 450 ( c )

So they spend a total of 450 coins.

Problem 4:

Exchange: 5 dollars= 500 c
Number of pineapples they can buy for $5 : 500/17 = 29,4

So they can buy about 29 pineapples.

Problem 5:

Total cost for adult and child tickets:

5*1.20=6$

20*50=1000 (c)=10$

6+10=16 $

So the total cost is $16.

Problem 6:

The number of blue cars is half the number of white cars: 16/2 = 8 ( blue cars )

The number of black cars is three times the number of blue cars: 8*3=24 ( black cars )

So there were 24 black cars that passed during the traffic survey.