(a^2-b^2)/(c-a) - найти, еслиa/3=b/2=c/5  и 5a +b -2c = 28

[latex] frac{a^2-b^2}{c-a}=frac{(a-b)(a+b)}{c-a}\\ frac{a}{3}=frac{b}{2}=frac{c}{5}\\ 5a+b-2c=28\\ 5a+frac{2a}{3}-frac{10a}{3}=28\\ 15a+2a-10a=28*3\\ a=12\\ b=2c-32\\ frac{2c-32}{2}=frac{c}{5}\\ c=20\\ b=8\\ frac{a^2-b^2}{c-a}=frac{80}{8}=10 [/latex]