It says find value of x?

Which property is illustrated by the following statement? if hxa rgi, then rgi hxa.

A) if $50000 is invested in a bank account that pays 9.3% of interest compounded on a six-monthly basis, how much money will be in the account after 3 and 12 years? b) if matusalen's father had put $2.0 in the bank when he was born and there, how long would matusalen have had to his death (969 years later) if the interest was 7% per year composed each month and weekly?

Iwill give ! if m∠a=59 and m∠3=81°, what is m∠b? m∠b= _[blank]_°