(8x+5)/7=12/24
(8x+5)/7=1/2
2(8x+5)=7
16x+10=7
16x=7-10
16x=-3
x=-16/3 

x=1,125

7 : (8x + 5) = 12 :24

8x+5= a

7 : a = 12:24

7: a = 1\2 -дробью

a= 7\1 x 1\2

a = 3   1\2= 3,5