[tex]2a+3b=7~si~a,b \geq 0 \Rightarrow 3b \leq 7,~dar~b \in N \Rightarrow b \in \{0;1;2\}. \\ \\ b=0 \Rightarrow 2a=7,~nu~convine. \\ b=1 \Rightarrow 2a+3=7 \Rightarrow \boxed{a=2}. \\ b=2 \Rightarrow 2a+6=7 \Rightarrow 2a=1,~nu~convine. \\ \\ Solutie:~\boxed{\boxed{a=2}~si~\boxed{b=1}}.[/tex]
