Help!!

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the distance between the center and any point on the circle is radius. double that and you get the diameter since diameter is doubled radius.

by distane formula, the radius is

sqrt( (x2-x1)^2 + (y2-y1)^2 ) = sqrt( (3-7)^2 + (-2 -1)^2) = sqrt(25) = 5

the diamter is 10

let x be volume of 1% and let y represent volume of 7% solution.

then the amount of minoxidil is

0.01x + 0.07y = 0.05(x+y)

but we have that x = 90 ml so

0.01(90) + 0.07y = 0.05(90+y)

0.9 + 0.07y = 4.5 + 0.05y

0.02y = 4.5-0.9

y = 3.6/ 0.02

y = 180 ml

she should add 180 ml of 7%