1)3,8hl= 380l
1800dl=180l
1700cl=17l
380-180-17=200-17= 183 l
2)2x/3 -5/6= 1 aducem la acelasi numitor
4x-5=6
4x=6+5
x=11/4
3)(15;21)=3
15=3*5
21=3*7
4)(3x;4)=2
(30+x ;4)=2 =>x=0
5)ΔABC, mas<A=90
mas<B=45 =>mas<C=90-45=45 grade <=>c1=c2
sin<B=45=√2/2
sin<B=AC/BC
AC/BC= √2/2 |²
AC²/BC²= 2/4
AC²/(AC²+AB²)=2/4
AC²/(AC²+AC²)=2/4
AC²/2AC²=2/4
1/AC²=2/4
AC²=4/2=2 =>AC=√2