Question

Mirela a cheltuit o suma de bani astfel in prima zi 25% din intreaga suma a doua zi 30% din suma initiala iar in a treia zi restul de 360 de lei . Care este suma initiala ?

Answer 1

$x\to suma \ initiala \\\\ 25\% \ din x =\frac{\not 25}{\not100}*x =\frac{1}{4}*x \to \frac{x}{4}-prima zi \\\\ x^{(4}-\frac{x}{4}=\frac{4x-x}{4}=\frac{3x}{4}-restul \\\\ 30\% \ din \ x =\frac{\not 30}{\not 100}*x = \frac{3}{10}*x \to \frac{3x}{10} -a \ doua \ zi \\\\ \frac{3x}{4}^{(10}-\frac{3x}{10}^{(4}=\frac{30x-12x}{40} \to \frac{18x}{40}-noul \ rest \\\\\\ \frac{18x}{40}=360 \\\\ x=\frac{360*40}{18} \\\\ x=20*40 \\\\ \boxed{x=800}$