Solve Complex Expression: 315÷(3/x)-(12x-4x÷(y/x))

To solve this problem, we need to address each term in the expression separately before combining them:

• Simplify $315:\frac{3}{x}$:
  This is equivalent to $315 \div \left(\frac{3}{x}\right)$, which can be rewritten using the property $a \div \frac{b}{c} = a \times \frac{c}{b}$. Thus, $315 \cdot \frac{x}{3} = 105x.$
• Simplify $12x-4x:\frac{y}{x}$:
  First, simplify $4x:\frac{y}{x}$.
  By the same property as above, we have: $4x \div \left(\frac{y}{x}\right) = 4x \cdot \frac{x}{y} = \frac{4x^2}{y}.$ Now, substitute back into the expression: $12x - \frac{4x^2}{y} = 12x - \frac{4x^2}{y}.$
• Subtract the second simplified expression from the first:
  $105x - (12x - \frac{4x^2}{y})$ Distribute the negative sign: $105x - 12x + \frac{4x^2}{y}.$ Combine like terms: $93x + \frac{4x^2}{y}.$

Therefore, the solution to the given expression is $93x + \frac{4x^2}{y}$.