\(7:\left(\frac{3,8\times x-57}{19}+3\right)=1,75\)
=> \(\frac{3,8\times x-57}{19}+3=7:1,75\)
=> \(\frac{3,8\times x-57}{19}+3=4\)
=> \(\frac{3,8\times x-57}{19}=4-3=1\)
=> \(3,8\times x-57=19\)
=> \(3,8\times x=19+57=76\)
=> \(x=76:3,8=20\)
Vậy x = 20.