13х-8=5х+16
7,8-4 (6-0.8х)=0,5 (7х+6)

1)13x-8=5x+1613x-5x=16+88x=24x=24:8x=3.2)7,8-4(6-0,8x)=0,5(7x+6)7,8-24+3,2x=3,5x+33,2x-3,5x=3+24-7,8-0,3x=19,2x=19,2:(-0,3)x=-64