Răspuns :
( 2×a+2)×3:4:7=18
( 2×a+2)×3:4=18×7
( 2×a+2)×3:4=126
( 2×a+2)×3=126×4
(2×a+2)×3=504
(2×a+2)=504:3
(2×a+2)=168
2×a=168-2
2×a=166
a=166:2
a=83
( 2×a+2)×3:4:7=18
( 2×a+2)×3:4=18×7
( 2×a+2)×3:4=126
( 2×a+2)×3=126×4
(2×a+2)×3=504
(2×a+2)=504:3
(2×a+2)=168
2×a=168-2
2×a=166
a=166:2
a=83