a) in ΔCAB,
CA²=BC²+AB²
CA²=16+9=25
CA=5
sin ∧CAB=CB/AC=4/5
tg∧ACB=AB/CB=3/4
4/5-3/4 =(4.4-3.5)/4.5=1/20
b)x-apartamente cu 2 camere
y-apartamente cu 3 camere
x+y=18, x=18-y
2x+3y=42
2(18-y)+3y=42
36-2y+3y=42
y=6 ap cu 3 camere
x=18-6=12 ap cu 2 camere
c) 2x-1-3x+2+x+3=4