[tex]a) \ A= \frac{b*h}{2} \\A=15\\ \frac{b*h}{2} =15\\ \frac{b*5}{2}=15\\b*5=2*15\\b= \frac{2*15}{5}\\b=2*3=6 \\ \\ \ b)A= \frac{b*h}{2}\\A=24\\ \frac{b*h}{2}=24\\ \frac{b*4,8}{2}=24\\ b*4,8=2*24\\b= \frac{2*24}{4,8}\\b=2*5=10\\b=h\\ \\ A= \frac{c_{1}*c_{2}}{2}\\ \frac{c_{1}*c_{2}}{2}=24\\c_{1}*c_{2}=2*24\\c_{1}*c_{2}=48 [/tex]