Question

решите систему 7х+4у=90; 5х-6у=20

Answer 1

7x+4y=90

5x-6y=20

 

x=90-4y/7

5(90-4y/7)-6y=20

450-20y-42y=140

450-62y=140

-62y=-310

y=5

x=90-4*5/7=10 

Answer 2

7x+4y=90
5x-6y=20
x=90-4y/7
5(90-4y/7)-6y=20
450-20y-42y=140
450-62y=140
-62y=-310
y=5
x=90-4*5/7=10