Answer: 
Step-by-step explanation:
Given
It takes 20 min and 30 min for a person and his friend to paint a wall individually i.e.
In 1 min they cover
part and
part of wall respectively.
If the work together, 1 minute work is

Time required will be reciprocal of it

Answer:
Step-by-step explanation:
Sec B
1) 5p⁻³ = 8*5⁻²
p⁻³ = 2³*5⁻²/5
p⁻³ =2³*5⁻³ { 1/a^m = a^-m}
p⁻³ = 5⁻³ /2⁻³ {a^m = 1/a^-m}
p⁻³ = (5/2)⁻³
p= 5/2
2) 4x² = 81
x² = 81/4
x² = 9² /2²
x² =(9/2)²
x = 9/2
3) 9^x/3 =81
9^x/3 = 9^2
Comparing the powers, x/3 = 2
x = 2*3 =6
x = 6
We can set up a system of equations:
x + y = 12
x - y = 4
Adding these two together:
2x = 16
x = 8
Substituting 8 in the first equation:
8 + y = 12
y = 4
Hope this helps!
90*1566=140,940 because how many means times