Question 1165445

D= Devon in 2020 
,J= Jamie in 2020
(D-7)= Devon in 2016
(D-7)= Devon in 2016

D+51=J
4*(D-7)=(J-7)

Try to subtract the two side of above equation together to remove J from right side.
D+51-(4D-28)=J-(J-7)
-3D+79=7 >>> 72=3D >>> D=24
And from first equation we have >>> J=D+51 >>> J=75