with intersecting chord lengths multiplying the 2 given lengths of one chord needs to equal the multiplication of the 2 lengths of the 2nd chord
so on chord FH you have 3.5 and 4.8
multiply those: 3.5 x 4.8 = 16.8
so now chord GI needs to equal 16.8
to find Y divide 16.8 by 2.4
y = 16.8 / 2.4 = 7
y = 7