Answer:
M = a + 24, where a is James' age and M is his mother's
Explanation:
a = James' age
His sister is 4 years younger than him:
a - 4 represents his sister's age.
His mother is 28 years older than his sister:
(a - 4) + 28
or a + 24 represents his mother's age
Let M = his mother's age
M = a + 24