[tex]\bf a)\\ \\ \it \overline{ab}\in\{10,\ \ 11,\ \ 12,\ ...\ .\ 99\} \Rightarrow 99-9=90 \ numere\ de\ forma\ \overline{ab},\\ \\ deci, \ vor\ fi\ 90\ de\ frac\c{\it t}ii.\\ \\ \bf b)\\ \\ \it 128=2^7, \ prin\ urmare\ vom\ determina\ c\hat ate\ frac\c{\it t}ii\ au\ numitorul\ par\\ \\ 10\leq 2k\leq98|_{:2} \Rightarrow 5\leq k\leq 49 \Rightarrow k=49-4=45\\ \\ Exist\breve a,\ a\d s adar,\ 45\ de\ frac\c{\it t}ii\ reductibile.[/tex]
