Can someone describe the equation for this function?

Two times a number plus three times another number equals 4. three times the first number plus four times the other number is 7. find the numbers

Your food costs are $5,500. your total food sales are $11,000. what percent of your food sales do the food costs represent?

Which sum or difference identity would you use to verify that cos (180° - q) = -cos q? a.) sin (a -b) = sin a cos b – cos a sin b b.) cos (a -b) = cos a cos b – sin a sin b c.) cos (a -b) = cos a cosb + sin a sin b d.) sin (a + b) = sin a cos b + cos a sin b