Which expression is equivalent to (7x+3)2

Need to increase the numbers of customers i talk to daily by 20% how many customers do i need to talk to if i talk to a average of 8 customers per hour during an 8 hour shift

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).

3.4a=57.8 what is the the value of a