Answer
$T_{equiv}$ = 33.0 - (33.0 - $T_{ambient}$) $\times$ (0.475 - 0.0126V + 0.240$\sqrt V$)
Work Step by Step
The given equation is:
$T_{equiv, °F}$= 91.4 - (91.4- $T_{ambient, °F}$) $\times$ (0.475 - 0.0203$V_{\frac{mi}{h}}$ + 0.304$\sqrt V_{\frac{mi}{h}}$
Knowing the conversion formulas to be:
(1) $T_{°F}$ = $T_{°C}$ $\times$ 1.8 + 32
(2) $V_{\frac{mi}{h}}$ = $V_{\frac{km}{h}}$ $\div$ 1.6
We can plug (1) and (2) into the original equation:
($T_{equiv, °C}$ $\times$ 1.8 + 32)= 91.4 - (91.4- ($T_{ambient, °C}$ $\times$ 1.8 + 32)) $\times$ (0.475 - 0.0203($V_{\frac{km}{h}}$ $\div$ 1.6) + 0.304$\sqrt (V_{\frac{km}{h}} \div 1.6)$
$T_{equiv, °C}$ $\times$ 1.8= 91.4 -32 - (91.4 -32 - $T_{ambient, °C}$ $\times$ 1.8 ) $\times$ (0.475 - 0.0126$V_{\frac{km}{h}}$ + 0.240$\sqrt V_{\frac{km}{h}}$
Dividing by 1.8 on both sides, and since (91.4 -32) $\div$ 1.8 = 33:
$T_{equiv, °C}$= 33.0 - (33.0 - $T_{ambient, °C}$ ) $\times$ (0.475 - 0.0126$V_{\frac{km}{h}}$ + 0.240$\sqrt V_{\frac{km}{h}}$
