<span>(x-18)•17=408
x-18=408:17
x-18=24
x=24+18
x=42
================
12:y+28=32
12:y=32-28
12:y=4
y=12:4
y=3
==============
18•(15-x)=216
15-x=216:18
15-x=12
x=15-12
x=3
===================
583:x-52=1</span>
583:x=1+52
583:x=53
x=583:53
x=11
23+3=26, 26+3=29, 29+3=32
31+5=36, 36+5=41, 41+5=46
42+4=46, 46+4=50, 50+4=54
Знаем, что дробь, у которой числитель = знаменателю равна единице, то есть: 13/13 = 1, 8/8=1, 12/12=1
7 10/13 -5 12/13 = (6+1) 10/13 - 5 12/13 = (6+13/13) 10/13 - 5 12/13 =
6 (13+10)/13 - 5 12/13 = 6 23/13 - 5 12/13 = (6-5) целых (23-12)/13 =
= 1цел 11/13
7- 5 12/13 = (6+1) - 5 12/13 = 6 13/13 - 5 12/13 = (6-5) цел (13-12)/13 =
=1 цел 1/13
7 10/13 - 5 2/3 = 7 (10*3)/(13*3) - 5 (2*13)/(3*13) = 7 30/39 - 5 26/39 =
(7-5) цел(30-26)/39 = 2 цел 4/39