Question

с простенькими уравнениями 1. x+3/5=13/20 2. x-3/20=4/5-1/2

Answer 1

1. x+3/5=13/20 |×20
4х+12=13
4х=1
х= 0,25
ответ: х=0,25

2. x-3/20=4/5-1/2
x-3/20=3/10 |×20
х-3= 6
х=9
ответ:х=9

Answer 2

$x + \frac{3}{5} = \frac{13}{20} \\ x + \frac{4 \times 3}{4 \times 5} = \frac{13}{20} \\ x + \frac{12}{20} = \frac{13}{20} \\ x = \frac{13}{20} - \frac{12}{20} \\ x = \frac{1}{20} = \frac{5}{100} = 0.05$
$x - \frac{3}{20} = \frac{4}{5} - \frac{1}{2} \\ x - \frac{3}{20} = \frac{4 \times 4}{5 \times 4} - \frac{1 \times 10}{2 \times 10} \\ x - \frac{3}{20} = \frac{16 - 10}{20} \\ x - \frac{3}{20} = \frac{6}{20} \\ x = \frac{6 + 3}{20} = \frac{9}{20} = \frac{45}{100} = 0.45$