Bonsoir
a) New York
68°F = (68-32)x 5/9 = 36 x 5/9 = 20°C
23°F = (23-32) x 5/9 = -9 x 5/9 = - 5°C
0° C = 0 x 1.8 +32 = 32°F
5°C = 5 x1.8 + 32 = 9 +32 = 41°F
10°C = 10 x 1.8 +32 = 18 +32 = 50°F
15°C = 15 x1.8 +32 = 27 + 32 = 59°F
20°C = 20 x 1.8 +32 = 36 +32 = 68°F