סוג שאלה : זרם.
V z {\displaystyle V_{z}} - מהירות זרם. כיוון הזרם : A C → {\displaystyle {\overrightarrow {AC}}}
A C → = C A → 4 ( V + V z ) = 6 ( V − V z ) 2 v + 2 v Z − 3 v − 3 v z 5 V Z = V V Z = v 5 {\displaystyle {\begin{aligned}&{\overrightarrow {AC}}={\overrightarrow {CA}}\\&4(V+V_{z})=6(V-V_{z})\\&2v+2v_{Z}-3v-3v_{z}\\&5V_{Z}=V\\&\color {blue}V_{Z}={\frac {v}{5}}\\\end{aligned}}}
3 4 ( 3 v + V Z ) = 12 3 4 ( 3 v + v 5 ) = 12 / : 3 3 v + v 5 = 16 15 v + v = 80 V = 5 {\displaystyle {\begin{aligned}&{\frac {3}{4}}(3v+{\color {blue}V_{Z}})=12\\&{\frac {3}{4}}(3v+{\frac {v}{5}})=12/:3\\&3v+{\frac {v}{5}}=16\\&15v+v=80\\&V=5\\\end{aligned}}}