Let ages of harry and peter be a yrs and b yrs respectively.
1 yr ago it had been :
harry = a-1 yrs
peter = b-1
Ratio = a-1/b-1 = 5/6
⇒ 6a - 6 = 5b - 5
⇒ 6a - 5b = 1 ............(1)
after 4 yrs it would have been :
harry = a+4
peter = b+4
ratio = a+4/b+4 = 6/7
⇒ 7a + 28 = 6b + 24
⇒ 6b - 7a = 4 ....(2)
solving (1) and (2)
a= 26 b = 31
Harry present age's 26 yrs
Peter present age 's 31 years