Write answers to the questions that are in the image.

see explanation

Step-by-step explanation:

He has incorrectly added/ subtracted the numerators/ denominators directly

To add/ subtract fractions we require them to have a common denominator

(a)

+

The lowest common multiple of 3 and 5 is 15

Change fractions to this denominator by multiplying numerator/denominator by the relevant value.

= +

= +

Now add the values on the numerators leaving the denominator

= =

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(b)

-

The lowest common multiple of 12 and 6 is 12

The first fraction already has a denominator of 12

Multiply the numerator/denominator of the second fraction by 2

= -

= -

= =