Question 1189930
Demola is two years older than deji and tobi is half of demolas age.The sum of their ages is 23.How old is deji?
<pre>Since Deji's age is required, we LET Deji's age be D
Then  Demola's is: D + 2, and Tobi's is: {{{(D + 2)/2}}}
With their ages summing to 23, we get: {{{matrix(2,3, D + D + 2 + (D + 2)/2, "=", 23, 2D + (D + 2)/2, "=", 21)}}}
4D + D + 2 = 42 ------ Multiplying by LCD, 2
5D = 40
Deji's age, or {{{highlight_green(matrix(1,5, D, "=", 40/5, "=", 8))}}}</pre>You're welcome, Tutor @Ikleyn, although I wasn't trying to correct you. If the "student" paid attention to your answer, he/she 
would've noticed that you gave Demola's age, and all he/she had to do was subtract 2 from that age to get Deji's age. That's all!