решите уравнения:14+6.2а+2.4а=69.9
14+6.2а+2.4а=69.9
6.2a+2.4a=-14+69.9
8.6a=55.9
a=55.9/8.6
a=6.5
14+6.2*6.5+2.4*6.5=69.9
69.9=69.9