40m+3n=13 {20m-7n=-5 решите систему уравнений

40m + 3n = 13
20m - 7n = - 5
Решение
- 40m + 14n = 10
17n = 23
n = 23/17 = 1 6/17
20m - 7•( 23/17 ) = - 5
20m = - 5 + ( 161/17 )
20m = - 5 + 9 8/17
20m = 4 8/17
m = 76/17 : 20
m = 38/170