Alan

There still are.  Click on the word Scientific at the right of the input line to see them.

Start by multiplying out the brackets on both sides of the equation:

0.3(6 + p) = 0.4(8 - p) 

0.3*6 +0.3*p = 0.4*8 -0.4*p

1.8 + 0.3*p = 3.2 - 0.4*p

Add 0.4*p to both sides and subtract 1.8 from both sides

0.3*p + 0.4*p = 3.2 - 1.8

Collect similar terms

0.7*p = 1.4

Divide both sides by 0.7

p = 1.4/0.7

p = 2

Start by letting the speed of the slower train be s km/hr. The speed of the other train is therefore s + 5 km/hr

Their relative speed (that is the speed of one as seen by the other) is the sum of these two; namely: 2s + 5 km/hr.

After two hours they will have travelled closer to each other by a distance (2s + 5)*2 km (because distance = speed*time).  Since they started 340km apart and are now only 30km apart, the combined distance they have travelled is 340 - 30 = 310 km.  So, we must have:

(2s + 5)*2 = 310

2s + 5 = 155

2s = 150

s = 75 km/hr

And the faster train's speed is 75+ 5 = 80 km/hr

(Edited to correct silly mistake!)

$$$\log{\sqrt{\frac{2t}{5w}}}=\frac{1}{2}(\log{2t}-\log{5w})=\frac{1}{2}(\log{2}+\log{t}-\log{5}-\log{w})$$$

Expanded about as far as it will go! 

$$$$\frac{-9+12i}{1+2i}=\frac{(-9+12i)(1-2i)}{(1+2i)(1-2i)}$$\\
$$ = \frac{-9-18i+12i+24}{1-2i+2i+4}$$\\
$$ = \frac{15-6i}{5}$$

$$$$ = 3-1.2i$$$$

Let the total money be x

Son gets x/3, daughter gets x/4, so amount left for wife is x - x/3 - x/4 = 12x/12 - 4x/12 - 3x/12 = 5x/12

 This must equal 20000.  5x/12 = 20000

Multiply both sides by 12/5 to get

x = 20000*12/5  = 4000*12 = 48000

Valid for -1<z<1

Intensity = current (I)

Tension = Voltage (V)

Resistance (R)

Ohm's law says V = I*R

V = 16*2 volts

V = 32 volts

$$Do you mean $\sum_{k=1}^{25}(3k+\frac{1}{4})$?\\
\\
If so, then this can be written as $$3\sum_{k=1}^{25}k+\sum_{k=1}^{25}\frac{1}{4}$$\\\\
This becomes $$3*\frac{25(25+1)}{2}+25*\frac{1}{4}$$\\
$$ = 975+6\frac{1}{4}$$
$$ = 981\frac{1}{4}$$

What are the statements from which you must choose?