Wh Mojave dessert is 25,000 sq miles

Two blends of tea are mixed to make a blend that will be sold at the fair. black tea sells for $2.20 per pound and orange pekoe tea sells for $3.00 per pound. how much of each should be used to obtain a 4lb blend selling for $2.50 per pound?

For what values of the variable x is the expression square root of 7x+14+ square root of 7-x a real number?

Math i have no idea how to do a and b