A same-phase divider shows load voltage falling as source impedance grows. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.
highlighted = computed this step
A small source impedance leaves three quarters on the load
Source impedance 2 ohms and load impedance 6 ohms put 3/4 of the input on the load.
16⋅86=12
Equal source and load split the input
Raising source impedance to 6 ohms makes the load share 1/2 and output 8 volts.
16⋅126=8
A large source impedance leaves one quarter on the load
Source impedance 18 ohms with the same load leaves share 1/4 and output 4 volts.