We are given the expression
[tex]\frac{10c+6}{7c\text{ -5}}[/tex]and we want to find the value of c for which this expression is undefined. Note that for rational expressions, they are undefined when we are dividing by 0. So, to find the value of c to which the expression is undefined, it suffices to find the value of c for which the denominator is 0. So we have the following equation
[tex]7c\text{ -5=0}[/tex]Now, we add 5 on both sides, so we get
[tex]7c=5[/tex]Finally, we divide both sides by 7. So we have
[tex]c=\frac{5}{7}[/tex]so when c=5/7 the expression is undefined
