3,5*(x+2 1/4) =14
3,5*(х+2 25/100)=14
3,5*(х+2,25)=14
3,5х+7,875=14
3,5х=14-7,875
3,5х=6,125
х=6,125:3,5
х=1,75
или
3,5*(x+2 1/4) =14
35/10*(х+9/4)=14
х*35/10+315/40=14
х*7/2+63/8=14
х*7/2=14-63/8
х*7/2=14-7 7/8
х*7/2=13 8/8-7 7/8
х*7/2=6 1/8
х=6 1/8:7/2
х=49/8*2/7
х=7/4
х=1 3/4