I need to know the steps to simplify 15.7 + (-3.45)

10.512*10^_3 write in proper scientific notation

There are 120 males and 180 females in Albany Tennis Club. Write the number of males to the number of females as a ratio in its simplest form.

A track and field playing area is in the shape of a rectangle with semicircles at each end. See the figure. The inside perimeter of the track is to be 1100 meters.

Show that the equation represents a circle by rewriting it in standard form, and find the center and radius of the circle. 5x^2 + 5y^2 + 10x - y = 0

Solve for the probability that a student is selected at random from a group of 20 students will draw a 6 from a bag with the numbers 1 though 15 in it. Show and explain all of your work.

At the local burger restaurant, you can get 4 value meals for $21.88. How much is each value meal?

A pack or cardinal flower seeds cost $4.00 and a pack of petunia flower seeds cost $2.50. You buy the same number of packs of each type of the flower and spend $39. How many packs of each do you buy?

Suppose the circumference of a circle is 24 pi. What is the radius of the circle?

One parrot species that feeds on large seeds nests is in the same tree as a parakeet that feeds on small seeds. How are the birds able to coexist?

A store owner buys backpacks at a certain price and sells them at a higher price. The difference is called the markup. If she pays $21 for a backpack and adds a 40% markup on the price she paid, what is the selling price?