Question 281130
Let the amount of whipping cream be W and let the amount of 2% milk be T.
1.{{{W+T=35}}} - Volume equation
2.{{{9W+2T=4*(W+T)=4(35)=140}}} - Concentration equation
Use eq. 1 to solve for W in terms of T.
{{{W+T=35}}}
{{{W=35-T}}}
Now substitute into eq. 2 and solve for T.
{{{9W+2T=140}}}
{{{9(35-T)+2T=140}}}
{{{315-9T+2T=140}}}
{{{-7T=-175}}}
{{{T=25}}}
Then from eq. 1,
{{{W=35-T=35-25=10}}}
10 gallons of whipping cream and 25 gallons of 2% milk.