[tex]a) a+54=69=\ \textgreater \ a=69-54=\ \textgreater \ a=15[/tex]
[tex]a+34=40=\ \textgreater \ a = 40-34=\ \textgreater \ a=6
[/tex]
[tex]b)20+b=90=\ \textgreater \ b=90-20=\ \textgreater \ b=70[/tex]
[tex]37+b=50=\ \textgreater \ b=50-37=\ \textgreater \ b=13[/tex]
[tex]c)c-42=8=\ \textgreater \ c=8+42=\ \textgreater \ c=52[/tex]
[tex]c-33=29=\ \textgreater \ c=29+33=\ \textgreater \ c=62[/tex]
[tex]d)80-d=55=\ \textgreater \ d=80-55=\ \textgreater \ d=25
[/tex]
[tex] 63-d=36;=\ \textgreater \ d=63-36=\ \textgreater \ d = 27[/tex]
