4/5x+x等于180

5x+6.9=34.

4 5x+6.9-6.9=34.4-6.

9 5x=27.

5 5x÷5=27.5÷5 x=5.

5 (2)(4.5+x)×2=13 9+2x=13 9+2x-9=13-9 2x=4 2x÷2=4÷2 x=2 (3)6x-4.8×0.4=5.28 6x-1.92=5.28 6x-1.92+1.92=5.28+1.92 6x=7.2 6x÷6=7.2÷6 x=1.2

4/5x+x等于180

4/5x+x=180

9/4x=180

x=180×4/9=80