How does the voltage at the R4(1) point become 3.78V?
Redrawing the circuit can make what's going on a little bit clearer. Just as Peter wrote, you can see here that R1 is in parallel with R3 and R4, so the voltage divider formula, in this case, would be helpful only after you reduce R1, R3 and R4 to their equivalent resistance. Call it Req, and then try to use the voltage divider formula. After that, you'd know what the voltage is across R2, and it would be possible to calculate the voltage on R3 and R4 individually. I'm sure you can follow it up from here :)



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