The percentage y (of total personal consumption) an individual spends on food is approximately y = 35x -0.25 percentage points (6.5 5 x 5 17.5),
where x is the percentage the individual spends on education. An individual finds that she is spending x = 7 + 0.2t percent of her personal consumption on education, where t is time in months
since January 1. Use direct substitution to express the percentage y as a function of time t (do not simplify the expression). (NOTE: January 1 is represented by t = 0.)
X(t) =
Use the chain rule to estimate how fast the percentage she spends on food is changing on May 1. (Round your answer to two decimal places.)
Specify the units.