Select the best estimate that would help you check the answer to 778×23 .

A.

700×30

B.

700×20

C.

800×20

D.

800×30

C: 800 x 20

Step-by-step explanation:

Basically, when you round 778 you see that the 7 and 8 are above 5, which means you round upwards. Therefore it would be best to round up to 800.

Then the 3 in 23 is below 5, meaning you round downwards. 20 Is the closest and best option.

So, C: 800 x 20 is best to do!

5x + 3y = - 4

step-by-step explanation:

the equation of a line in standard form is

ax + by = c ( a is a positive integer and b, c are integers )

express the line first of all in slope- intercept form

y = mx + c ( m is the slope and c the y-intercept )

to calculate m use the gradient formula

m = ( y₂ - y₁ ) / ( x₂ - x₁ )

with (x₁, y₁ ) = (7, - 3) and (x₂, y₂ ) = (4, - 8)

m = = -

y = - x + c ← is the partial equation

to find c substitute either of the 2 points into the partial equation

using (4, - 8 ), then

- 8 = - + c ⇒ c = -

y = - x - ← in slope-intercept form

multiply all terms by 3 to eliminate the fractions

3y = - 5x - 4 ( add 5x to both sides )

5x + 3y = - 4 ← in standard form