1)in prima zi 20/100*x
in a doua zi 2/5*(80/100*x)
in a treia zi 15km
20x/100+16x/50+15=x
20x/100+32x/50+1500=100x aducem la acelasi numitor
20x+32x+1500=100x
52x-100x=-1500
48x=1500
x=31.25
2)R+M=40ani
M=4*R
inlocuim
R+4*R=40
5*R=40
R=8ani
atunci mama are 40-8=32
8*4=32