Answer:
Part A: x+y=75 is the 1st linear equation
y=25+x
Part B:
x+y=75
x+(25+x)=75
2x=50
x=25
she spends 25 mins running
part c : no because if she spends 45 mins
then x+y=70
but x+y=75
she spends 50 mins dancing
