Răspuns:
a)
0,2 = 2/10 = 1/5
1/5 • (x - 2/5) - 1/5 = 1/5
1/5 • (x - 2/5) = 2/5
x - 2/5 = 2/5 • 5
x - 2/5 = 2
x = 2 + 2/5
x = 7/5
b)
0,4 = 4/10 = 2/5
[1/2 + (2/5 + x) • 1/5] • 10/7 = 1
1/2 + (2/5 + x) • 1/5 = 7/10
(2/5 + x) • 1/5 = 7/10 - 1/2
(2/5 + x) • 1/5 = 1/5
2/5 + x = 1
x = 1 - 2/5
x = 3/5