qn 11:

24 sweets 'same' as 18 chocs

i.e., 8 sweets 'same' as 6 chocs

if he bought 8 sweets, it's like he bought 6 chocs.

thus, he could buy another 12 chocolates.

qn 28:

2/7 + 1/5 = 17/35

so, he had 1 - 17/35 = 18/35 of money left.

and this is $18.

so, 1/35 of money is $1

thus, he had $35 at first.

qn 15:

compare ratio in receipe: F : S : B = 5 : 3 : 2

to what she had: F : S : B = 625 : 620 : 1000 = 125 : 124 : 200

so, she should use up all her flour (and she had excess of other two):

(625 / 200) x 20 = 62.5

From the given options, select (1) 60 cookies as max then.

hope this helps.