To solve the problems, you need to isolate/get the variable (t, p, x, a....) by itself in the equation. To do so, you need to multiply the inverse of the fraction to get rid of the fraction and get the variable by itself. [The inverse of a fraction is basically flipping the fraction or switching the numerator and the denominator]
[I can't tell if the variables are in the denominator or not, but variables can not be in the denominator, so you need to multiply the variable to get it on the other side of the equation]
1.
Multiply the inverse of 2/5 on both sides
t = 50
2.
Multiply the inverse of 7/8 to get "p" by itself
p = 64
Do the same for the other problems if the variable is not in the denominator.
13. 2t + 6 = 106 Subtract 6 on both sides
2t + 6 - 6 = 106 - 6
2t = 100 Divide 2 on both sides
t = 50
If you're confused or want to check any of the problems just let me know(and possibly clarify where the variable is - denominator/numerator)