During a sale , customer spent exactly $260 on sweaters , jeans and shoes . Each sweater cost $25, each pair of jeans costs $50, and each pair of shoes cost $20. The customer bought twice as many sweaters as pair of shoes . The customer purchased 10 items. Let x= the number of sweaters, y=the number of pairs of jeans and z= the number of pairs of shoes you should buy. Write the systems of equations .

Aresearch study is studying the effects of a new drug for osteoporosis alzheimer's disease (ad) for women above the age of 65 years. a group of individuals with osteoporosis is randomized into two groups. one group is treated conventionally, and the second group is treated with the new medication. assessments are made at 3, 6, 12, 36, and 48 months. the conventionally treated group is assessed for ad using a serum blood test, and the treatment group is assessed for ad using a pet radiotracer that binds to beta-amyloid plaques. in comparing these 2 trial arms, the authors of the study may encounter which type of bias? a. selection bias on the risk of developing b. measurement bias c. confounding bias d. recall bias e. lead-time bias