Find the value of x
I give you 10 points if you help

Ricardo ran the 400 meter race 3 times his fastest time was 54.3 seconds his slowest time was 56.1 seconds if his average time was 55.0 seconds what was his time for the third race

2/3(-6y+9x) expand each expression using the distributive property

For what values of a is the sum of the fractions 2a−1 / 4 and a−1 /3 positive?