Answer:
at 6:00 pm the temperature reaches 18 degrees
Step-by-step explanation:
since the temperature increases linearly with the time then
t = t₀ + m * (T-T₀)
where
t = time at temperature T
t₀= initial time at temperature T
m= increase in time with temperature
T₀ = initial temperature
therefore replacing values
t = 7 hour + 1 hour/2°C* [18°C-(-4°C)] = 18 hour → 18:00 = 6:00 pm
thus at 6:00 pm the temperature reaches 18 degrees