Question

mr mensah starts a job with an annual salary of $6400 which increases by $240 every year after working for eight years mr mensah is promoted to a new post with an annual salary of 9500 which increases by $360 every year calculate mr mensah salary in the fifteenth year of service and mr mensah total earnings at the end of the fifteenth year of service

Answer 1

The way I read it, you have 8 terms of the first AP, with a = 6400 and d=240
plus 7 terms of a second AP with a = 9500 and d=360

The 15th year would be the 7th term of series #2
term7 = 9500+6(360) = ....

Use your sum of terms formula to find the two sums and add them.

Answer 2

Yes

Answer 3

Please solve it with full details