X- 9 = 21:5
X- 9 = 4,2
x = 4,2 + 9
x = 13,2
X : 3 = 1,248 : 4
X : 3 = 0,312
x = 0,312 x 3
x = 0,936
x - 9 = 4,2
x = 4,2 + 9 =13,2
x : 3 = 0,312
x = 0,312 x 3 = 0,936
\(x-9=21:5\\ x-9=4,2\\ x=4,2+9\\ x=13,2\)
\(x:3=1,248:4\\ x:3=0,312\\ x=0,312\times3\\ x=0,936\)