[tex] \frac{a}{4}+ \frac{a}{3}+ \frac{12}{1}=a-3 \\ \\ \frac{7a}{12}+ \frac{12}{1}= \frac{a-3}{1} \\ \\ \frac{a-3}{1}- \frac{7a}{12}= \frac{12}{1} \\ \\ \frac{12a-36}{12} - \frac{7a}{12}= \frac{12}{1} \\ \\ \frac{5a-36}{12}= \frac{12}{1}\ facem \ produsul\ incrucisat \\ 5a-36=12*12 \\ 5a-36=144 \\ 5a=180 \\ a=36 [/tex]
sper ca te-am ajutat
