5. For any two numbers $x, y$, the operation “*” is defined as: $x * y=\frac{4 \times x \times y}{m \times x+3 \times y}$ (where $m$

is a fixed number), if $1 * 2=1$, then $m=$ $\qquad$ , $3 * 12=$ $\qquad$ _.
$\mathrm{m}=2 \quad 3 * 12=\frac{24}{7}$

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