(2670+6(240-43×x)×5)÷50+72×3=336 ,

Держите, все просто)))

(2670+6*(240-43*x)*5)/50+216=336
(2670+6*(240-43*x)*5)/50=336-216
(2670+6*(240-43*x)*5)/50=120
(2670+6*(240-43*x)*5)=120*50
(2670+6*(240-43*x)*5)=6000
2670+6*(1200-215x)=6000
2670+(7200-1290x)=6000
7200-1290x=6000-2670
7200-1290x=3330
1290x=7200-3330
1290x=3870
x=3870/1290
x=3