x*(7+9-1-5)=790
x*10=790
x=790 chia 10
x=79
\(x\times7+x\times9-x-x\times5=790\)
\(\Leftrightarrow x\times7+x\times9-x\times1-x\times5=790\)
\(\Leftrightarrow x\times\left(7+9-1-5\right)=790\)
\(\Leftrightarrow x\times10=790\)
\(x=790\div10\)
\(x=79\)
Đáp số : X = 79