Gisele trains 7 days per week for a biathlon. she covers a total of 20 miles cycling and running each day. gisele cycles a total of 105 miles each week, and runs a certain number of miles per week. if she cycles the same number of miles each day and runs the same number of miles each day, the equation 1/7(105+r)=20 represents the situation. which describes the solution, r , to this equation?

Let
x> total of miles cycling each week
r> total of miles running each week

we know that
20*7=140 miles> total of miles cycling and running each week
x+r=140> equation 1
x=105>  equation 2

substitute equation 2 in equation 1
[105]+r=140> divide by 7 both sides> (1/7)*[105+r]=20

where
105/7> 15 miles>  total of miles cycling each day

r=140-105> r=35---> total of miles running each week
35/7> 5 miles---> total of miles running each day

the answer is
r describes the total of miles running each week