`c` 

$\frac{60+67+x}{3}$ $\geq$ `70`

$\frac{127+x}{3}$ `-` `70` $\geq$ `0`

$\frac{127+x}{3}$ `-` $\frac{210}{3}$  $\geq$ `0`

$\frac{127+x - 210}{3}$ $\geq$ `0`

$\frac{x - 83}{3}$ $\geq$ `0`

$\frac{x}{3}$ `-` $\frac{83}{3}$ $\geq$ `0`

$\frac{x}{3}$ $\geq$  $\frac{83}{3}$ 

`x` $\geq$ `3` `.` $\frac{83}{3}$ 

`x` $\geq$ 83