a)5+10=30-x
=>15=30-x
=>x=30-15
=>x=15
b)10+40=90-x
=>50=90-x
=>x=90-50
=>x=40
\(5+10=30-x\)
\(15=30-x\)
\(x=15\)
\(10+40=90-x\)
\(50=90-x\)
\(x=40\)
5 + 10 = 30 - x
15 = 30 - x
30 - x = 15 ( đổi vế )
x = 30 - 15
x = 15
10 + 40 = 90 - x
50 = 90 - x
90 - x = 50 ( đổi vế )
x = 90 - 50
x = 40
nha bn
5+10=30-x
<=>15=30-x
<=>x=30-15
<=>x=15
10+40=90-x
<=>50=90-x
<=>x=90-50
<=>x=40
5 + 10 = 30 - x
15. = 30 - x
x. = 30 - 15
x. = 15
10 + 40 = 90 - x
50. = 90 - x
x = 90 - 50
x. = 40