` a) ` ` 4.(x - 3) = 7 `
` => 4x - 12 = 7^1 - 1^{2020} `
` => 4x - 12 = 7 - 1 `
` => 4x - 12 = 6 `
` => 4x = 18 `
` => x = 9/2 `
` b) ` ` 2^{x+1} . 2^{2019} = 2^{2020} `
` => 2^{x + 1} = 2^1 `
` => x + 1 = 2 `
` => x = 1 `
` c) ` ` 3^2 x + 4 - 5^2 = 5.1 - 5.2^2 + 13x `
` => 9x + 4 - 25 - 5 + 5.4 - 13x = 0 `
` => 9x - 13x + 4 - 4 - 25 + 20 = 0 `
` => -4x - 5 = 0 `
` => -4x = 5 `
` => x = -4/5 `
` d) ` ` 3^2 x = 2023^{3^1} `
` => 9x = 2023^3 `
` => x = \frac{2023^3}{9} `