Equivalence relation: 1 monthly coal consumption× (1-20%) = February coal consumption.
Equation: x × (1-20%) = 1.6.
x = 1.6 \80 %
X=2
Train speed 106 km, 35% faster than cars. How many kilometers does this car travel per hour?
Equivalence relation: car speed × (1+35%) = train speed.
Equation:
X×( 1+35%)= 106
x = 106 \ 135%
X=78.5