a) 20+x=678
x=678-20
x=658
Vậy x=658
b) x.15=450
x=450:15
x=30
Vậy x=30
c) 2197: x=13
x= 2197:13
x=169
Vậy x=169
d) 2784-x=324
x= 2784-324
x=2460
Vậy x=2460
a) 20 + x = 678 .
=> x = 678 - 20 .
=> x = 658 .
b) x . 15 = 450 .
=> x = 450 : 15 .
=> x = 30 .
c) 2197 : x = 13 .
=> x = 2197 : 13 .
=> x = 169 .
d) 2784 - x = 324.
=> x = 2784 - 324 .
=> x = 2460 .
\(a,20+x=678\) \(b,x.15=450\)
\(x=678-20\) \(x=450\div15\)
\(x=658\) \(x=30\)
\(c,2197\div x=13\) \(d,2784-x=324\)
\(x=2197\div13\) \(x=2784-324\)
\(x=169\) \(x=2460\)