Clara has pennies and quarters in her purse. She counts a total of 28 coins. If the total value of the coins is 76 cents, which system of equations can be used to determine the number of pennies and the number of quarters? Assume p represents the number of pennies and q represents the number of quarters. p + q = 28. p + 25 q = 76.
p + q = 28. 25 p + q = 76.
p + q = 76. p + 25 q = 28.
p + q = 76. 25 p + q = 28.

1. there are 25 students who started computer programming in elementary school and 25 students who started computer programming in middle school. the first group had a mean final project grade of 95% and the second group had a mean final project grade of 92%. the line plot shows the differences after 10 rerandomizations. determine whether the difference in the means of the two groups is significant based on the line plot. explain your answer.

For f(x) = 3x+1 and g(x) = x2 - 6, find (g/f)(x)

Ariana starts with 100 milligrams of a radioactive substance. the amount of the substance decreases by 20% each week for a number of weeks, w. the expression 100(1−0.2)w finds the amount of radioactive substance remaining after w weeks. which statement about this expression is true? a) it is the difference between the initial amount and the percent decrease. b) it is the difference between the initial amount and the decay factor after w weeks. c) it is the initial amount raised to the decay factor after w weeks. d) it is the product of the initial amount and the decay factor after w weeks.