When using substitution to solve a system of education, how can you tell when a system has no solution

What is the effect on the graph of the parent function f(x) = x when f(x) is replaced with 3f(x)? a) shifts the line 3 units up b) shifts the line 3 units down c) increases the slope of the line by a factor of 3 d) decreases the slope of the line by a factor of 3

Find the value of x for which line a is parallel to line b

Tom drove 206 miles in 3.9 hours. estimate his average speed.