Tina rolls a dice what is the probability that she rolls a 1 b3 c4 d 3 or 4

Brady has a 20 year fixed rate mortgage for $215,500 with monthly payments of 1,305.89.the annual interest rate is 4%. what is the total cost of the principal and interest for this loan rounded to the nearest dollar

When using the linear combination metho e linear combination method to solve a system of linear equations, the four options are:

I'm confused on this could anyone me and show me what i need to do to solve it.