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Решите задачу:

$\frac{x}{7} =\frac{x}{3} +8\\\\ (\frac{x}{7}) =(\frac{x}{3} +8)\\\\ (\frac{x}{7})*21 =(\frac{x}{3} +8)*21\\\\ \frac{x}{7}*21 =\frac{x}{3}*21 +8*21\\\\ \frac{x}{7}*21 =\frac{x}{3}*21 +8*21\\\\ \frac{x*21}{7} =\frac{x*21}{3} + 8*21\\\\ \frac{x*3*7}{7*1} =\frac{x*3*7}{3*1} + 8*21\\\\ \frac{x*3}{1} =\frac{x*7}{1} + 8*21\\\\$

$x*3 =x*7 + 8*21\\\\ 3*x =7*x + 8*21\\\\ 3*x -7*x=7*x + 8*21-7*x\\\\ x*3 -7*x=7*x + 8*21-7*x\\\\ x*(3-7)=7*x-7*x+8*21\\\\ x*(-4)=0*x+8*21\\\\ x*(-4)=8*21\\\\ \frac{x*(-4)}{-4}=\frac{8*21}{-4}\\\\ x=-\frac{8*21}{4}=-2*21=-42$