Answer:
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
= -
= -
= =