Idk what it means, sorry and good luck
The answer is that x equals 15
Im pretty sure the answer is 92.0 becauese
if you do 10.5x3.5 5x5=25 5x0+2=7 5x1=5 so that will be 57.5 then your going to do 3x5=15 3x0+1=4 3x1=3 that equals 34.5 then your going to add 57.5 +34.5
= 92.0
For two complex numbers

and

, the product is

That is, you multiply the moduli and add the arguments. You have

and

, so the product is
Distance = speed x time
time = distance/speed
= 340/85
= 4h