ex 5 (un biciclist a parcurs un drum astfel in prima zi………)

Explicație pas cu pas:
10/100 × x + 30/100 × x + 42 = x
1/10 × x + 3/10 × x + 42 = x
4/10 × x +42 = x
x - 4/10 × x = 42
10/10×x - 4 /10 × x = 42
6/10 × x = 42
x = 42 : 6/10
x = 42 × 10/6
x = 420/6
x = 70