I am not sure if this is too late for your CA. Nevertheless, hope this still serves to help in your learning.

(1) .........croissants (c)........ tarts

before: ........4 u.....................1 u

change: .....-1 u...................-0.8 u

[note: 0.25 = 1/4]

after: ...........3 u....................0.2 u

(a) that is, 3u - 0.2 u --> 98

so that, 1u --> 35

and, 0.8u --> 28

so Wendy gave away 28 egg tarts.

(b) 3u --> 105 butter croissants were left.

(2) let cost of a pear be $1u; then a mango cost $(1u + 3.7)

thus, 5 pears + 5 mangoes --> $(5u + 5u + 18.5)

and, 8 pears + 4 mangoes --> $(8u + 4u + 14.8)

(a) 10u + 18.5 = 12u + 14.8

then, 2u = 3.7

thus, 1u = 1.85. That is, a pear cost $1.85.

(b) a mango cost $(1.85 + 3.70) = $5.55.

(3) is the question correct? It should be easy to solve from the context, though the numerical figures won't divide nicely.

(4) Let there be n alarm clocks.

under the old pricing, he should collect $(15.5n + 2.3 x 30) = $(15.5n + 69)

under the new pricing, he would collect $(16n + 60)

now, 15.5n + 69 = 16n + 60

therefore, 0.5n = 9

so that, n = 18

So, James sold 18 alarm clocks.

(5) Inder saves $1.50; Zoe saves $2.50.

Let Zoe save for n days.

(a) then, 2.5n = 1.5(n + 10) + 12

so that, 1n = 15 + 12 = 27

Thus Inder has been saving for 27 + 10 = 37 days.

(b) Zoe has 27 x $2.50 = $67.50 now.

Cheerio, hope this is useful.