Well, Reese, this is a problem that has two unknowns, Mr. Maria's present age and Mrs. Maria's present age. With two unknowns we need to have two equations to solve it.
Let x=Mr. Maria's present age
y=Mrs. Maria's present age
Eq. I: x=y+5 Mr. Maria is 5 years older than his wife
Eq. II: x-5=(4/3)(y-5) Five years ago Mr. Maria was (x-5) years old and Mrs. Maria was (y-5) years old.
Using the substitution method we can solve Eq. II for y by substituting the value for x in terms of y from Eq. I:
x-5=(4/3)(y-5) original equation
(y+5)-5=(4/3)(y-5) substitute y+5 for x
y-(4/3)y=(-20/3) subtract (4/3)y from both sides to isolate the y term
(-3)(-1/3)y=(-3)(-20/3) multiply both sides by -3
Using this value for y in Eq. I we can find x:
x=y+5 Eq. I
x=20+5 putting value of 20 in for y
Therefore, their present ages are Mr. Maria is 25 and his wife is 20. To find out how old they will both be in 8 years you just need to add 8 to their present ages. I'll leave that for you!