Răspuns :
a+b=90
b=a:5
=>
a=90-b
=>>
b=(90-b):5
b=18-b:5
[tex]b = 18 - \frac{1}{5} b \\ \\ 5b = 90 - b \\ \\ 6b = 90 \\ \\ b = 15[/tex]
=>
a+15=90
a=75
a+b=90
b=a:5
=>
a=90-b
=>>
b=(90-b):5
b=18-b:5
[tex]b = 18 - \frac{1}{5} b \\ \\ 5b = 90 - b \\ \\ 6b = 90 \\ \\ b = 15[/tex]
=>
a+15=90
a=75