Răspuns :
{[(a+5)×2]-10}:7=14
[(2a+10)-10]:7=14
(2a+10-10):7=14
2a:7=14
a=49
verificare
{[(a+5)×2]-10}:7=14
{[(49+5)×2]-10}:7=14
(54×2)-10):7=14
(108-10):7=14
98:7=14
14=14
deci a=49
[(2a+10)-10]:7=14
(2a+10-10):7=14
2a:7=14
a=49
verificare
{[(a+5)×2]-10}:7=14
{[(49+5)×2]-10}:7=14
(54×2)-10):7=14
(108-10):7=14
98:7=14
14=14
deci a=49