The speed of a river current is 7 mph. if a boat travels 20 miles downstream in the same time that it takes to travel 10 miles upstream find the speed of the boat in still water

  21 mph

Step-by-step explanation:

The relationship between time, speed, and distance is ...

  time = distance/speed

The speed downstream is b+7 if the boat's speed is b. The speed upstream is b-7, and the times in each direction are equal. This means ...

  20/(b+7) = 10/(b-7) . . . . . . time in each direction are the same

  20(b-7) = 10(b+7) . . . . . . . cross multiply

  (20-10)b = 7(10+20) . . . . . add 7(20)-10b

  b = 7(20 +10)/(20 -10) = 21 . . . . mph

The speed of the boat in still water is 21 mph.

step-by-step explanation:

ok so im not 100% sure but you would start by adding 5.1t and 1.9t beacuse they have the same variable. that is 7t.   then add -3.6 + 1.2 which is -2.4

so then keep that as -2.4 + 7t. i apologize if this is incorrect. best luck on your test < 3

simplifying

5(x + -6) = 2(x + 3)

reorder the terms:

5(-6 + x) = 2(x + 3)

(-6 * 5 + x * 5) = 2(x + 3)

(-30 + 5x) = 2(x + 3)

reorder the terms:

-30 + 5x = 2(3 + x)

-30 + 5x = (3 * 2 + x * 2)

-30 + 5x = (6 + 2x)

solving

-30 + 5x = 6 + 2x

solving for variable 'x'.

move all terms containing x to the left, all other terms to the right.

add '-2x' to each side of the equation.

-30 + 5x + -2x = 6 + 2x + -2x

combine like terms: 5x + -2x = 3x

-30 + 3x = 6 + 2x + -2x

combine like terms: 2x + -2x = 0

-30 + 3x = 6 + 0

-30 + 3x = 6

add '30' to each side of the equation.

-30 + 30 + 3x = 6 + 30

combine like terms: -30 + 30 = 0

0 + 3x = 6 + 30

3x = 6 + 30

combine like terms: 6 + 30 = 36

3x = 36

divide each side by '3'.

x = 12

simplifying

x = 12

this should .