7 = 2n - 2
n= a number so twice a number is 2n and 7 is 2 less than twice this number.
Answer:

Step-by-step explanation:
The LCM of 14, 21 and 6 is 42
We require to change the fractions to fractions with a denominator of 42
+
+ 
=
+
+
← add the numerators, leaving the denominator
= 
=
← divide both values by 2
=
← in simplest form
The answer is b 7 unit reflexes