How to find the thevenin equivalent resistance and voltage?
simulate this circuit – Schematic created using CircuitLab
The solution for calculating the thevenin resistance is
\$(5//20)+2+1+2=9\$,i can understand this methodm,just let the current source become open circuit,and let the voltage source become short circuit
However,i can't understand the solution for calculating the thevenin voltage
\$V_{th}=5 \times 2 +25-25\times \frac{20}{20+5}=15V\$
Can anyone tell me why can the author just write the \$V_{th}\$ formula above?