Question 981522
You're missing punctuation in your question, so I'm making some assumptions.
J = M + 10
.5 M = .25J
Substitute the known value of J from the first equation into the second.
.5M = .25(M+10)
.5M = .25M + 2.5
.25M = 2.5
Multiply each side by 4 to get a whole M
1M = 10
Let's check.
If Michelle is 10, then Joan is 10 years older than that, or 20.
Is 1/4 of 20 the same as 1/2 of 10?
5 = 5
Success.
Michelle is 10 and Joan is 20.