Answer:
Step-by-step explanation: multiply the number of books Martina read 3 times.
Answer:
4 hours and 30 minutes.
Step-by-step explanation:
270÷60=4.5
Answer:
7x+9y=45
Step-by-step explanation:
Standard equations always mean that you have to get x and y on one side so that they equal the coefficient.
Do this by adding the fraction that is combined with x to the other side where y is. The equation should now read 
Standard form cannot have fractions, so now you must multiply by the denominator (9) on both sides of the equation in order to cancel it out. Don't forget to multiply EACH variable by 9. This leads you to the answer.