1) а -15×30=320
а- 450=320
а=320+450
а=770
770-450=320
320=320
2) (х+240)×3-360=540
3х+720-360=540
3х +360=540
3х=540-360
3х=180
х=180:3
х=60
3×60 +360=540
180+360=540
540=540
3) 876+у+9.869=78.000
у+10.745 =78.000
у=78.000-10.745
у=67.255
67.255+ 10.745 =78.000
78.000 =78.000