Х-15=2(х+10)
х-15=2х+20
-15=2х+20-х
-15=х+20
-35=х
х=-35
Задуманное число = -35
7 - 3 = 5 - х; 4 = 5 -х ; х = 5-4; х = 1
х + 7 = 5 + 3; х +7 = 8; х = 8 - 7; х = 1
х - 3 = 5 - 1; х -3 = 4; х = 4 + 3; х = 7
х + 5 = 7 + 1 ; х + 5 = 8; х = 8 - 5; х = 3
х - 5 = 3 - 1; х - 5 = 2; х = 5 + 2; х = 7
15/35 =3/7, 30/70=3/7,
92/100=23/25, 23/25
15/50=3/10, 3/10
88/16=11/2, 11/2
56/8=7
63/210=9/70
42/51=14/17, 126/153=14/17, 14/17, 70/85=14/17
36/84=9/21
121/11=11, 33/11=11
48/102=24/51
Прямоугольный треугольник