1) 1.3 * (7 - x) = 0.39;
7 - x = 0.39 : 1.3;
7 - x = 0.3;
x = 7 - 0.3;
x = 6.7;
2) (x + 4) : 0.4 = 21;
x + 4 = 21 * 0.4;
x + 4 = 8.4;
x = 4.4.
1) 1.3 * (7 - x) = 0.39;
7 - x = 0.39 : 1.3;
7 - x = 0.3;
x = 7 - 0.3;
x = 6.7;
2) (x + 4) : 0.4 = 21;
x + 4 = 21 * 0.4;
x + 4 = 8.4;
x = 4.4.