1) 15у-8у=714 9ч+ч=500 10х+х=702 6х+3х-х=6400 6у+2у+25=65

15y-8y=714

7y=714

y=714:7

y=102

9x+x=500

10x=500

x=500:10

x=50

10x+x=702

11x=702

x=702:11

x=63  9/11

6x+3x-x=6400

8x=6400

x=6400:8

x=800

6y+2y+25=65

8y=65-25

8y=40

y=40:8

y=5