Which of the following completes the formula of cos (a + B) = A. sin a cos B - cos a sin B
B. sin a cos B + cos a sin B
O C. cos a cos B- sin a sin B
OD. cos a cos B+ sin a sin B

Angie has saved 3/8 of the amount she needs to buy a bike. clive has saved 7/10 of the amount he needs to buy a skateboard. what is the difference between clive's and angie's fraction of savings?