If interpolation is forbidden (which the multiple choice answer options seem to indicate)...................
Calculate MBRW from the most conservative wind component, i.e. 10 Kt Headwind,
Calculate V Speeds according to the environmental conditions and the actual weight, i.e. 15 Kt Headwind.
Boeing's recommendation for most B777 operations -
(1) Obtain the RTOW from the Airport Analysis according to the most conservative wind,
(2) Enter the actual wind into the FMC, (which makes the V1 allowances that you allude to), and use the FMC speeds.
Airline policy may vary.
Regards,
Old Smokey